EPUB Content Problems

Overview

The EPUB Error Scanner checks the following:

To learn more about each kind of check and its associated notifications, read the sections below.

Problem Classifications

EPUB Content Problems are classified as follows:

TypeColor CodeDescription
ErrorA serious problem according to relevant EPUB specifications (or specifications relevant to EPUB Content Documents, such as the HTML Standard).

Problems of this type may prevent your EPUB from being opened by EPUB Reader software and/or cause issues when applying for publication.
WarningA minor problem—or something that is not recommended—according to relevant EPUB specifications (or specifications relevant to EPUB Content Documents, such as the HTML Standard).

Problems of this type should not prevent your EPUB from being opened by EPUB Reader software.

Book Metadata

Checks a Book’s metadata, being the attributes and values entered in Book Settings.

TitleTypeMessage
Book Metadata is Incomplete<VALUE> is required for publication.
Book Metadata is IncompleteThis setting expands on <VALUE>. Without <VALUE>, it will be ignored.
Book Metadata is IncompleteThis setting expands on <VALUE-A> and <VALUE-B>. Without <VALUE-A> and <VALUE-B>, it will be ignored.
Book Metadata is Incomplete<VALUE-A> is required when <VALUE-B> is present.
Book Metadata Inconsistency FoundThe format of Identifier (<VALUE>) does not match the Identifier Scheme (<SCHEME>). Please check that the Identifier and Identifier Scheme settings are correct.

Naming

Checks for duplicate names for Parts, Documents and Chapters.

TitleTypeMessage
Duplicate TitleThe <ITEM> has the same title as another <ITEM>. This may confuse the reader (depending on your compilation settings) and will cause problems for some kinds of export. Consider giving your <ITEM> another title.

Container

Checks container.xml for conformance with the EPUB Specifications.

TitleTypeMessage
Container Format ErrorNo <container> element can be found in container.xml. Container.xml must include a <container> element.
Container Namespace ErrorElement <container> contains an empty ‘xmlns‘ attribute. The <container> element’s ‘xmlns‘ attribute should contain a valid namespace (in case an EPUB Reader does not use a default).
Container Namespace ErrorThe <container> element’s ‘xmlns‘ attribute contains an unexpected value. Check the ‘xmlns‘ attribute and confirm that the namespace is correct.
Container Namespace ErrorElement <container> has no ‘xmlns‘ attribute. The <container> element’s ‘xmlns‘ attribute should contain a valid namespace (in case an EPUB Reader does not use a default).
Container Format ErrorContainer.xml contains multiple <container> elements. Container.xml should have only one <container> element.
Container Format ErrorNo <rootfiles> element can be found in container.xml. Container.xml must include one or more <rootfiles> elements.
Container Format ErrorMultiple <rootfiles> elements were found in container.xml. Container.xml can include only one <rootfiles> element.
Container Format ErrorThe <rootfiles> element has no <rootfile> child elements. Container.xml must include one or more <rootfile> elements in <rootfiles>.
Empty Attribute FoundA <rootfile> element must have a ‘full-path‘ attribute containing the URL of an OPF file.
Duplicate URL Destination FoundThe URL in each <rootfile> element’s ‘full-path‘ attribute must be unique. A duplicate URL was found: <URL>
Unexpected Value FoundThe <rootfile> element’s ‘full-path‘ attribute specifies a destination that is invalid: <PATH>
Required Attribute MissingA <rootfile> element must have a ‘full-path‘ attribute containing the URL of an OPF file.
Empty Attribute FoundA <rootfile> elements’s ‘media-type‘ attribute cannot be empty.
Unexpected Value FoundA <rootfile> element’s ‘media-type‘ attribute must have the value ‘application/oebps-package+xml‘.
Required Attribute MissingA <rootfile> element must have a ‘media-type‘ attribute (with the value ‘application/oebps-package+xml‘).
Required Attribute MissingElement <link> has no ‘href‘ attribute. The ‘href‘ attribute is required.
Unclosed Element FoundElement <NAME> is not closed. Elements with content must have both a start and an end tag (e.g. <p> and </p>) or, in the case of elements without content, a forward slash before the tag’s end (e.g. <br />).

OPF

Checks links from container.xml to the OPF and OPF integrity.

TitleTypeMessage
OPF is OrphanedNo <rootfile> elements in container.xml refer to this OPF. None of the resources listed in the OPF’s <manifest> element will be included in the EPUB.
Package Format ErrorThe file contains invalid XML (or is empty).
Unclosed Element FoundElement <NAME> is not closed. Elements with content must have both a start and an end tag (e.g. <p> and </p>) or, in the case of elements without content, a forward slash before the tag’s end (e.g. <br />).
Package Format ErrorThe first element in an OPF file must be <package>.
Package Version ErrorThe <package> element’s ‘version‘ attribute is empty. The <package> element’s ‘version‘ attribute must have the value ‘<VERSION>‘ to indicate compliance with version <VERSION> of the EPUB Specification.
Package Version ErrorThe <package> element’s ‘version‘ attribute does not match your Book’s EPUB Version setting. The <package> element’s ‘version‘ attribute must have the value ‘<VERSION>‘ to indicate compliance with version <VERSION> of the EPUB Specification.
Package Version ErrorThe <package> element has no ‘version‘ attribute. The <package> element must have a ‘version‘ attribute with the value ‘<VERSION>‘ to indicate compliance with version <VERSION> of the EPUB Specification.
Package Unique-Identifier ErrorThe <package> element’s ‘unique-identifier‘ attribute is empty. The <package> element’s ‘unique-identifier‘ attribute must have the value of an ‘id‘ belonging to a <dc:identifier> element in <metadata>.
Package Unique-Identifier ErrorThe <package> element’s ‘unique-identifier‘ attribute must have the value of an ‘id‘ belonging to a <dc:identifier> element in <metadata>. No <dc:identifier> elements with an ‘id‘ attribute can be found.
Package Unique-Identifier ErrorThe <package> element’s ‘unique-identifier‘ attribute is missing. The <package> element’s ‘unique-identifier‘ attribute must be present and have the value of an ‘id‘ belonging to a <dc:identifier> element in <metadata>.
Package Format ErrorThe <metadata> element must be the first child of <package>. Element <NAME> has taken its place. Move or delete the <NAME> element.
Package Format ErrorThe <metadata> element must be the first child of <package>. No <metadata> element can be found.
Package Format ErrorThe <manifest> element must be the second child of <package>. Element <NAME> has taken its place. Move or delete the <NAME> element.
Package Format ErrorThe <manifest> element must be the second child of <package>. No <manifest> element can be found.
Package Format ErrorThe <spine> element must be the third child of <package>. Element <NAME> has taken its place. Move or delete the <NAME> element.
Package Format ErrorThe <spine> element must be the third child of <package>. No <spine> element can be found.
Package Contains an Duplicate ElementsElement <package> must contain only one <NAME> child element. More than one <NAME> element was found.

OPF <metadata> Element

Checks the content and integrity of the OPF <metadata> tag.

TitleTypeMessage
Metadata is IncompleteElement <metadata> does not have a <NAME> child element. The <NAME> element is required.
Metadata is IncompleteElement <metadata> does not have a <meta> child element with the ‘dcterms:modified‘ property set. A <meta> element with the ‘dcterms:modified‘ is required.
Metadata Namespace Error

(version 3.1)
Element <metadata> contains an empty ‘xmlns:opf‘ attribute. The ‘xmlns:opf‘ attribute must have a value when the <metadata> element contains one or more elements with ‘opf‘ prefixed attributes (such as ‘opf:alt-rep‘, ‘opf:alt-rep-lang‘, ‘opf:file-as‘ etc.).
Metadata Namespace Error

(version 3.1)
Element <metadata> contains an ‘xmlns:opf‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.idpf.org/2007/opf.
Metadata Namespace Error

(version 3.1)
Element <metadata> has no 'xmlns:opf‘ attribute. The ‘xmlns:opf‘ attribute is required when the <metadata> element contains one or more elements with ‘opf‘ prefixed attributes (such as ‘opf:alt-rep‘, ‘opf:alt-rep-lang‘, ‘opf:file-as‘ etc.).
Metadata Namespace ErrorElement <metadata> contains an empty ‘xmlns:dc‘ attribute. The ‘xmlns:dc‘ attribute must have a value when the <metadata> element contains one or more elements with ‘dc‘ prefixes (such as <dc:title>, <dc:identifier>, <dc:language> etc.).
Metadata Namespace ErrorElement <metadata> contains an ‘xmlns:dc‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://purl.org/dc/elements/1.1/
Metadata Namespace ErrorElement <metadata> has no ‘xmlns:dc‘ attribute. The ‘xmlns:dc‘ attribute is required when the <metadata> element contains one or more elements with ‘dc‘ prefixes (such as <dc:title>, <dc:identifier>, <dc:language> etc.).

OPF <metadata> Child Elements

Checks the content and integrity of elements within the <metadata> tag, such as <dc:identifier>, <dc:title> etc.

TitleTypeMessage
Metadata is IncompleteElement <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute must have a value when the element includes the ‘<ATTRIBUTE>‘ attribute.
Metadata is IncompleteElement <NAME> has no ‘<ATTRIBUTE-A>‘ attribute. The ‘<ATTRIBUTE-A>‘ attribute is required when the element includes the ‘<ATTRIBUTE-B>‘ attribute.
Metadata Attribute is OrphanedElement <NAME> includes an ‘<ATTRIBUTE-A>‘ attribute, but does not include an ‘<ATTRIBUTE-B>‘ attribute. The ‘<ATTRIBUTE-A>‘ attribute expands on the ‘<ATTRIBUTE-B>‘ attribute. Without the ‘<ATTRIBUTE-B>‘ attribute, the ‘<ATTRIBUTE-A>‘ attribute will be ignored.
Metadata Link IncompleteElement <link> contains an empty ‘media-type‘ attribute. The ‘media-type‘ attribute must have a value when the element includes the ‘href‘ attribute that specifies a remote resource.
Metadata Link IncompleteElement <link> contains no ‘media-type‘ attribute. The ‘media-type‘ attribute must be present when the element includes the ‘href‘ attribute that specifies a remote resource.
Metadata is IncompleteElement <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute must have a value.
Deprecated Value FoundElement <NAME> contains an attribute (‘<ATTRIBUTE>‘) that specifies a deprecated value (<VALUE>). Consider changing the value to something else.
Unexpected Value FoundElement <NAME> contains an ‘<ATTRIBUTE>‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: <LIST>.
Metadata is IncompleteElement <NAME> has no ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute is required.
Empty Attribute FoundElement <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute should have a value when present.
Unexpected Value FoundElement <NAME> contains an ‘xml:lang‘ attribute that specifies an unknown language code (<CODE>). Check that the language is valid.
Unexpected Value FoundElement <NAME> contains a <meta> child element that ‘refines‘ an unknown element. Check that a <metadata> element with an ‘id‘ of ‘<ID>‘ exists within the <collection>.
Unexpected Value FoundElement <NAME> contains a <meta> child element that ‘refines‘ an unknown element. Check that a <meta> element with an ‘id‘ of ‘<ID>‘ exists.
Deprecated Value FoundElement <NAME> contains a deprecated value (<VALUE>) for the <PROPERTY> property. Consider changing the value to something else.
Unexpected Value FoundElement <NAME> contains an ‘<ATTRIBUTE>‘ attribute that specifies an unexpected value (<VALUE>). Please check that the specified value is correct.
Unexpected Attribute FoundThe <NAME> element contains an unexpected attribute (<ATTRIBUTE>). Check whether the <NAME> element needs the ‘<ATTRIBUTE>‘ attribute.
Metadata Contains an Unexpected ElementElement <metadata> contains an unexpected child element (‘<NAME>‘). Consider deleting the element.
Metadata Contains an Duplicate ElementsElement <metadata> must contain only one <NAME> child element. More than one <NAME> element was found.
Metadata Contains an Empty ElementElement <NAME> is empty. Enter a value between the element’s opening and closing tags.

OPF <metadata> Child Elements: <meta> specific

Checks the content of the <meta> tag.

TitleTypeMessage
OPF <meta> Element Found in <collection>An OPF2 <meta> element was detected within a <manifest> element within a <collection>. The OPF2 <meta> element is not allowed in this context.
Obsolete Element FoundElement <metadata> contains an OPF2 <meta> element. The OPF2 <meta> element is obsolete.
Unexpected Value FoundElement <NAME> contains a property attribute that defines an unrecognized expression (<EXPRESSION>). Check that the expression is correct.
Superseded Attribute Found

(version 3.1)
Element <meta> contains a ‘refines‘ attribute. The ‘refines‘ attribute is deprecated. It is replaced by the ‘duration‘, 'opf:alt-rep‘, ‘opf:authority‘, ‘opf:file-as‘, ‘opf:role‘, ‘opf:scheme‘ and ‘opf:term‘ attributes. Use at your own risk.
Empty Element FoundElement <NAME> contains no value. The ‘<NAME>‘ element must enclose a value within its opening and closing tags.
Unexpected Value FoundElement <NAME> contains an unexpected value (<VALUE>). Allowed values for <NAME> elements with ‘property‘ attributes with the ‘<EXPRESSION>‘ expression are: <LIST>.
Invalid Value Found

(version 3.2)
Element <NAME> contains an attribute (‘<ATTRIBUTE>‘) that specifies a value (<VALUE>) that cannot be used in conjunction with the ‘refines‘ attribute. Consider changing the value to something else.

OPF <manifest> Element

Checks the content and integrity of the <manifest> element.

TitleTypeMessage
Empty Attribute FoundElement <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute should have a value when present.
Duplicate Element ID FoundAn element’s ‘id‘ attribute must be unique. You have included an ‘id‘ attribute in an element (<NAME>) that contains a duplicate of another element’s ‘id‘ (<ID>).
Manifest Format ErrorThe <manifest> element must have one or more <item> child elements.
Manifest Item IncompleteElement <item> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute must have a value.
Superseded Value FoundYou have included a ‘media-type‘ attribute in an <item> element with a value of ‘application/x-dtbncx+xml‘. This media type refers to the superseded NCX. Usage of superseded EPUB features is not recommended. Use at your own risk.
File Extension Does Not Match Media TypeElement <manifest> contains an <item> child element with a <MEDIA-TYPE>media-type‘ that references a content document (<PATH>) with an unexpected file extension (<EXT>). A <FILE-TYPE> filename should use the file extension <EXT>.
File Extension Does Not Match Media TypeElement <manifest> contains an <item> child element with a <MEDIA-TYPE>media-type‘ that references a content document (<PATH>) without a file extension. A <FILE-TYPE> filename should use the file extension <EXT>.
Fallback RequiredYou have included a ‘media-type‘ attribute in an <item> element with a value that does not match a Core Media Type. If this is not intended, check the spelling of the media type. Otherwise, a ‘fallback‘ attribute will be required.
Manifest Item IncompleteElement <item> has no ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute is required.
Manifest Item IncompleteYou have included a ‘fallback‘ attribute in an <item> element that is empty.
Fallback is RecursiveYou have included a ‘fallback‘ attribute in an <item> element that falls back to itself.
Fallback is FaultyYou have included a ‘fallback‘ attribute in an <item> element that refers to another <item> element that contains one or more errors. Choose another <item> element (or fix the <item> element’s errors).
Fallback is InvalidYou have included a ‘fallback‘ attribute in an <item> element that has an invalid value. A ‘fallback‘ attribute’s value must equal the ‘id‘ attribute of an <item> element within the <manifest>.
Fallback is MissingAll <item> element’s that use a Non-Core Media Type must have a ‘fallback‘ attribute. The ‘fallback‘ attribute is missing.
Empty Attribute FoundElement <item> contains an empty ‘properties‘ attribute. The ‘properties‘ attribute should have a value when present. Allowed values are: <LIST>. These values can be used in combination (but must be separated by spaces).
Unexpected Value FoundElement <item> contains an ‘properties‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: <LIST>.
Manifest Properties Does Not Match ContentElement <manifest> contains an <item> child element that includes the ‘switch‘ value in its ‘properties‘ attribute, but which references a resource without the <epub:switch> element within its content. Consider removing the ‘switch‘ property or adjusting the resource’s content.
Manifest Properties Does Not Match ContentElement <manifest> contains an <item> child element that includes the ‘svg‘ value in its ‘properties‘ attribute, but which references a resource without embedded SVG within its content. Consider removing the ‘svg‘ property or adjusting the resource’s content.
Manifest Properties Does Not Match ContentElement <manifest> contains an <item> child element that includes the ‘mathml‘ value in its ‘properties‘ attribute, but which references a resource without embedded MathML within its content. Consider removing the ‘mathml‘ property or adjusting the resource’s content.
Manifest Properties Does Not Match ContentElement <manifest> contains an <item> child element that includes the ‘scripted‘ value in its ‘properties‘ attribute, but which references a resource without the <script> element within its content. Consider removing the ‘scripted‘ property or adjusting the resource’s content.
Media Overlay is RecursiveElement <item> contians a ‘media-overlay‘ attribute that references the element’s own ‘id‘ (<ID>).
Media Overlay is InvalidYou have included a media-overlay’ attribute in an <item> element that has an invalid value. An ‘media-overlay‘ attribute’s value must equal the ‘id‘ attribute of an <item> element within the <manifest>.
Unexpected Element FoundThe <manifest> element contains an unexpected element (<NAME>). The <manifest> element should only contain <item> children.
Multiple Cover Images FoundOnly one <item> element can have a ‘properties‘ value that includes ‘cover-image‘.
Navigation MissingOne <item> element with a ‘properties‘ value that includes ‘nav‘ is required. No matching <item> elements can be found in the <manifest> element.
Multiple Navigation Properties FoundOnly one <item> element can have a ‘properties‘ value that includes ‘nav‘.

Checks the content and integrity of documents referenced from <item> child elements of OPF <manifest> with a ‘properties‘ attributes that include ‘nav‘.

TitleTypeMessage
Unexpected Navigation Media TypeAn <item> element in the <manifest> with a ‘nav‘ property uses an unexpected ‘media-type‘ (<MEDIA-TYPE>). The ‘application/xhtml+xml‘ media type must be used.
Unexpected Navigation ResourceAn <item> element in the <manifest> with a ‘nav‘ property references a non-XHTML resource (<URL>). Check whether the resource is correct. If the correct resource is referenced in ‘href‘, then change the item’s file extension to ‘xhtml‘.
Navigation Format ErrorA ‘toc<nav> element is empty. A ‘toc<nav> element should contain an optional heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA ‘toc<nav> element contains one or more unexpected child elements. A ‘toc<nav> element can only contain an optional heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA ‘page-list<nav> element is empty. A ‘page-list<nav> element should contain an optional heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA ‘page-list<nav> element contains one or more unexpected child elements. A ‘page-list<nav> element can only contain an optional heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA ‘page-list<nav> element contains one or more nested <ol> elements. Only one <ol> element is allowed.
Navigation Format ErrorThe <ol> element must have one or more <li> child elements.
Navigation Format ErrorWithin a <nav> element, the <li> element must have a <span> or <a> element. No child elements were found.
Navigation Format ErrorA <span> element cannot appear within <nav> element’s <li> descendants unless it is followed by an <ol> element. No <ol> element was found.
Navigation Format ErrorElement <a> has no ‘href‘ attribute. The ‘href‘ attribute is required.
Navigation Format ErrorA <li> element within a <ol> element of a <nav> element contains one or more unexpected child elements: <LIST>. A <li> element in this context must contain a <span> or <a> element.
Navigation Format ErrorWithin a <nav> element, the <li> element must have a <span> or <a> element. Further, where the <span> element appears, it must be followed by an <ol> element. This pattern was not satisfied. Instead, the following sequence was found: <LIST>
Navigation Format ErrorA ‘landmarks<nav> element is empty. A ‘toc<nav> element should contain an optional heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA ‘landmarks<nav> element contains one or more unexpected child elements. A ‘landmarks<nav> element can only contain an optional heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorAn <a> element child of a ‘landmarks<nav> element possesses an ‘epub:type‘ attribute. All <a> child elements of a ‘landmarks<nav> element must have an ‘epub:type‘ attribute.
Navigation Format ErrorA <nav> element is empty. A <nav> element that has a type other than ‘toc‘, ‘page-list‘ or ‘landmarks‘ must contain a heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA <nav> element contains one or more unexpected child elements. A <nav> element that has a type other than ‘toc‘, ‘page-list‘ or ‘landmarks‘ can only contain a heading element (<h1>, <h2>, <h3>, <h4>, <h5>, <h6>) and a single <ol> element (in that order).
Navigation Format ErrorA <nav> element contains one or more ‘embedded content‘ child elements that do not have a ‘title‘ attribute. When an ‘embedded content‘ child element does not have an intrinsic text alternative, it must have a ‘title‘ attribute.
Navigation Format ErrorA <nav> element contains one or more <li> child elements that have a zero-length text label. All <a> and <span> descendants of <li> elements must have a readable text label (or, in the case of non-textual descendant elements, a non-empty ‘title‘ or ‘alt‘ attribute).
Navigation Item Order Does Not Match SpineThe position of the <nav> element resource at path <PATH> is different to that indicated in the <spine>. The order of <li> elements contained within ‘toc‘ and ‘page-list<nav> element must follow the order of Content Documents in the <spine>.
Navigation Resource not found in SpineThe <nav> element resource at path <PATH> was not found in the <spine> element of an OPF file that is referenced in container.xml. The order of <li> elements contained within ‘toc‘ and ‘page-list<nav> element must follow the order of Content Documents in the <spine>.
Navigation Format ErrorA <nav> element contains no ‘epub:type‘ attribute. If this is not intended, please add the ‘epub:type‘ attribute to the <nav> element.
Navigation Format ErrorAn EPUB Navigation Document must have a <nav> element that carries the ‘epub:type‘ attribute set to ‘toc‘. No such elements were found.
Navigation Format ErrorAn EPUB Navigation Document must have exactly one <nav> element that carries the ‘epub:type‘ attribute set to ‘toc‘. Multiple matching elements were found.
Navigation Format ErrorAn EPUB Navigation Document can have only one <nav> element with the ‘epub:type‘ attribute set to ‘page-list‘. Multiple matching elements were found.
Navigation Format ErrorAn EPUB Navigation Document can have only one <nav> element with the ‘epub:type‘ attribute set to ‘landmarks‘. Multiple matching elements were found.
Navigation Format ErrorThe file contains invalid XML (or is empty).

OPF <spine> Element

Checks the content and integrity of the OPF <spine> element.

TitleTypeMessage
Empty Attribute FoundElement <spine> contains an empty ‘<ATTRIBUTE>‘ attribute. The ”<ATTRIBUTE>‘ attribute should have a value when present.
Empty Attribute FoundElement <spine> contains an empty ‘page-progression-direction‘ attribute. The ‘page-progression-direction‘ attribute should have a value when present. Allowed values are: <LIST>.
Duplicate Element ID FoundAn element’s ‘id‘ attribute must be unique. You have included an ‘id‘ attribute in an element (<NAME>) that contains a duplicate of another element’s ‘id‘ (<ID>).
Unexpected Value FoundElement <spine> contains an ‘page-progression-direction‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: <LIST>.
Superseded Attribute FoundYou have included a ‘toc‘ attribute in an <itemref> element. This attribute refers to <manifest> items that represent the superseded NCX. Usage of superseded EPUB features is not recommended. Use at your own risk.
Spine Format ErrorThe <spine> element must have one or more <itemref> child elements.
Spine ID Reference EmptyElement <itemref> contains an empty ‘idref‘ attribute. The ‘idref‘ attribute must have a value.
Manifest Item Reference is FaultyYou have included an ‘idref‘ attribute in an <itemref> element that refers to an <item> element that contains one or more errors.
Spine References an Unknown ResourceYou have included an ‘idref‘ attribute in an <itemref> element that has an invalid value. An ‘idref‘ attribute’s value must equal the ‘id‘ attribute of an <item> element within the <manifest>.
Spine ID Reference MissingElement <itemref> has no ‘idref‘ attribute. The ‘idref‘ attribute is required.
Empty Attribute FoundElement <itemref> contains an empty ‘id‘ attribute. The ‘id‘ attribute should have a value when present.
Empty Attribute FoundElement <itemref> contains an empty ‘linear‘ attribute. The ‘linear‘ attribute should have a value when present. Allowed values are: <LIST>.
Empty Attribute FoundElement <itemref> contains an empty ‘properties‘ attribute. The ‘properties‘ attribute should have a value when present. Consult your EPUB documentation for allowed values (which are too numerous to list here, and can be used in combination).
Unexpected Value FoundElement <itemref> contains a ‘linear‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: <LIST>.
Unexpected Value FoundElement <itemref> contains a ‘properties‘ attribute that specifies an unexpected value (<VALUE>). Consult your EPUB documentation for allowed values (which are too numerous to list here, and can be used in combination).
Deprecated Value Found

(version 3.1)
Element <itemref> contains an attribute (‘properties‘) that specifies a deprecated value (rendition:spread-portrait). Consider changing the value to something else.
Conflicting Values FoundYou have included a ‘properties‘ attribute in an <itemref> element (<CONFLICTING-VALUE>) that cannot be used in combination with the other values specified in the attribute: <VALUES>.
Prepaginated Content ErrorEach EPUB Content Document referenced from a <spine> item that has the ‘pre-paginated‘ value set must contain a ‘viewport‘ (for XHTML) or a ‘viewbox‘ (for SVG) dimension expression. The resource at path ‘<PATH>‘ does not meet this requirement.
Unexpected Element FoundThe <spine> element contains an unexpected element (<NAME>). The <spine> element should only contain <itemref> children.
Unexpected Element FoundElement <spine> must include one <itemref> child element whose ‘linear‘ attribute value is set to ‘yes‘ (or is otherwise omitted, causing the default value of ‘yes‘ to be applied). This requirement was not satisfied.

OPF <guide> Element

Checks for presence of OPF <guide> element.

TitleTypeMessage
Deprecated Element Found

(version 3.0.1)
The <package> element contains a <guide> child element. The <guide> element is deprecated.
Obsolete Element Found

(version 3.1)
The <package> element contains a <guide> child element. The <guide> element is obsolete. Remove the <guide> element from the OPF.

OPF <bindings> Element

EPUB version-specific checks for the OPF <bindings> element.

TitleTypeMessage
Bindings Format Error

(version 3.0.1)
The <bindings> element must have one or more <mediatype> child elements.
Multiple Bindings Found

(version 3.0.1)
The <package> element contains multiple <bindings> child elements. A <package> element can only have one <bindings> child element.
Empty Attribute Found

(version 3.0.1)
Element <mediatype> contains an empty ‘media-type‘ attribute. The ‘media-type‘ attribute must have a value.
Core Media Type Re-definition Not Allowed

(version 3.0.1)
You have included a ‘media-type‘ attribute in a <mediatype> element that re-defines a Core Media Type. Core Media Types cannot appear in the ‘media-type‘ attribute of a <mediatype> element.
Media Type Not Unique

(version 3.0.1)
You have included a ‘media-type‘ attribute in a <mediatype> element that has already been defined. Each content type defined the <bindings> element’s <mediatype> child elements must be unique.
Required Attribute Missing

(version 3.0.1)
Element <mediatype> has no ‘media-type‘ attribute. The ‘media-type‘ attribute is required.
Empty Attribute Found

(version 3.0.1)
Element <mediatype> contains an empty ‘handler‘ attribute. The ‘handler‘ attribute must have a value.
Media Type References Unscripted Manifest Item

(version 3.0.1)
You have included a ‘handler‘ attribute in a <mediatype> element that references an <item> in the <manifest> that does not include ‘scripted‘ in its ‘properties‘ attribute.
Media Type References Non-XHTML Manifest Item

(version 3.0.1)
You have included a ‘handler‘ attribute in a <mediatype> element that references an <item> in the <manifest> that is not an XHTML Content Document. The <item> must have a ‘media-type‘ attribute with an ‘application/xhtml+xml‘ value.
Media Type References an Unknown Manifest Item

(version 3.0.1)
You have included a ‘handler‘ attribute in an <mediatype> element that has an invalid value. A ‘handler‘ attribute’s value must equal the ‘id‘ attribute of an <item> element within the <manifest>.
Required Attribute Missing

(version 3.0.1)
Element <mediatype> has no ‘handler‘ attribute. The ‘handler‘ attribute is required.
Obsolete Element Found

(version 3.1)
The <package> element contains a <bindings> child element. The <bindings> element is obsolete. Remove the <bindings> element from the OPF.

OPF <collection> Element

Checks the content and integrity of the OPF <collection> element.

TitleTypeMessage
Collection Format ErrorElement <collection> contains an empty ‘role‘ attribute. The ‘role‘ attribute must have a value. Allowed values are: <LIST> or a valid URL (used in combination).
Collection Format ErrorThe <collection> element’s ‘role‘ attribute appears to specify an invalid value: <VALUE>. Allowed values are: <LIST> or a valid URL (used in combination).
Collection Format ErrorElement <collection> has no ‘role‘ attribute. The ‘role‘ attribute is required.
Empty Attribute FoundElement <collection> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute should have a value when present.
Duplicate Element ID FoundAn element’s ‘id‘ attribute must be unique. You have included an ‘id‘ attribute in an element (<collection>) that contains a duplicate of another element’s ‘id‘ (<ID>).
Unexpected Value FoundElement <collection> contains an ‘xml:lang‘ attribute that specifies an unknown language code (<CODE>). Check that the language is valid.
Unexpected Value FoundElement <collection> contains an ‘dir‘ attribute that specifies an unexpected value (<VALUES>). Allowed values are: <LIST>.
Collection Format ErrorThe <collection> element must have one or more <metadata>, <collection> or <link> child elements.
Collection Format ErrorThe <collection> element must contain, at minimum, one <collection> element or one <link> element. Neither were found.
Collection Format ErrorThe <collection> element must contain an optional <metadata> element, and one <collection> element or one <link> element, at minimum. This pattern was not satisfied. Instead, the following sequence was found: <LIST>
Forbidden Attribute FoundA <link> element within a <metadata> descendant of a <collection> element uses the ‘refines‘ attribute. A ‘refines‘ attribute must not be attached to a <link> element in this context.
Empty Attribute FoundElement <link> contains an empty ‘href‘ attribute. The ‘href‘ attribute must have a value.
Required Attribute MissingElement <link> has no ‘href‘ attribute. The ‘href‘ attribute is required.
Empty Attribute FoundElement <link> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute should have a value when present.
Duplicate Element ID FoundAn element’s ‘id‘ attribute must be unique. You have included an ‘id‘ attribute in an element (<link>) that contains a duplicate of another element’s ‘id‘ (<ID>).
Deprecated Value FoundElement <link> contains an attribute (‘rel‘) that specifies a deprecated value (<VALUE>). Consider changing the value to something else.
Unexpected Value FoundElement <link> contains an ‘rel‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: <LIST>.

Checks for the existence of certain links and link integrity.

TitleTypeMessage
Orphaned Resource FoundAll resources in the Code section of your project must be linked in an OPF file (and the OPF file must be linked in container.xml). This resource does not meet this requirement. It will not be included in the EPUB.
Linked Resource Not Listed in SpineA reference to the resource at path ‘<PATH>‘ cannot be found in the rendition’s <spine>. All resources that are hyperlinked from another resource in the <spine> must also be listed in the <spine>.
Empty Attribute FoundThe <NAME> element’s ‘<ATTRIBUTE>‘ attribute appears to be empty.
External Links Not AllowedExternal links are not allowed from <NAME> elements in this file.
External Link UnreachableThe <NAME> element’s ‘<ATTRIBUTE>‘ attribute specifies a destination that is unreachable (<URL>).
Invalid Link FoundThe <NAME> element’s ‘<ATTRIBUTE>‘ attribute specifies a destination that is invalid (<URL>).
Invalid Link FoundThe <NAME> element’s ‘<ATTRIBUTE>‘ attribute specifies a local destination that is invalid (<URL>).
Forbidden Link Destination FoundA <link> element includes a ‘href‘ attribute that references a resource that is listed in the <manifest>. This is not allowed.

XHTML Content Documents

Checks the content and integrity of XHTML resources.

TitleTypeMessage
HTML Format Error
The page has no <html> element. All XHTML pages must have the following elements: <html>, <head>, <body>.
HTML Format Error
The page has no <head> element. All XHTML pages must have the following elements: <html>, <head>, <body>.
HTML Format Error
The page has no <body> element. All XHTML pages must have the following elements: <html>, <head>, <body>.
Required Attribute Missing
Element <link> has no ‘href‘ attribute. The ‘href‘ attribute is required.
Orphaned CSS Class Found
The page’s markup contains references to a class (<CLASS>) that does not appear in the page’s inline styles or linked CSS files.
Style Elements Found
The page’s markup contains <style> elements. This is not recommended. Consider moving the relevant style directives into a CSS file.
Inline Styles Found
The page’s markup contains tags that use inline styles (e.g. ‘style‘ attributes). This is not recommended. Consider moving the relevant style directives into a CSS file.
Named Entities Found
The page’s markup contains named HTML entities (like &amp;). Named HTML entities are not supported.
Unencoded Symbols Found
The page’s markup contains unencoded symbols that might confuse XHTML-parser logic in some EPUB reader software. These symbols should be encoded into HTML entities.
Resource Has No Media Type
No Media Type is set for this resource. It cannot be included in the EPUB’s manifest (see container.xml).
Unclosed Element Found
Element <NAME> is not closed. Elements with content must have both a start and an end tag (e.g. <p> and </p>) or, in the case of elements without content, a forward slash before the tag’s end (e.g. <br />).
Forbidden Attribute Found
Element <NAME> contains one or more ‘epub:type‘ attributes. The ‘epub:type‘ is not allowed in the <head> element or its descendants.
Empty Attribute Found
Element <NAME> contains an empty ‘epub:type‘ attribute. The ‘epub:type‘ attribute should have a value when present.
Deprecated Value Found
Element <NAME> contains an attribute (‘epub:type‘) that specifies a deprecated value (<VALUE>). Consider changing the value to something else.
Deprecated Value Found
Element <NAME> contains an attribute (‘epub:type‘) that specifies a deprecated value (<VALUE>). Consider changing the value to: <CURRENT-VALUE>.
Unexpected Value Found
Element <NAME> contains an ‘epub:type‘ attribute that specifies an unexpected value (<VALUE>). Consult your EPUB documentation for allowed values (which are too numerous to list here).
Element Placement Error
Element <NAME> contains an <epub:switch> child element. The <epub:switch> should only be used in HTML5 Flow Content and inline content.
Empty Attribute Found
Element <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute should have a value when present.
Switch Format Error
Element <NAME> is the first child of <epub:switch>. An <epub:case> element must be the first child of an <epub:switch>.
Switch Format Error
Element <NAME> is the last child of <epub:switch>. An <epub:default> element must be the last child of an <epub:switch>.
Empty Attribute Found
Element <epub:case> contains an empty ‘id‘ attribute. The ‘id‘ attribute should have a value when present.
Empty Attribute Found
Element <epub:case> contains an empty ‘required-namespace‘ attribute. The ‘required-namespace‘ attribute must have a value.
Unexpected Value Found
The <epub:case> element’s ‘required-namespace‘ attribute specifies a destination that is invalid.
Required Attribute Missing
Element <epub:case> has no ‘required-namespace‘ attribute. The ‘required-namespace‘ attribute is required.
Unexpected Content Found
Element <epub:case> appears to contain unexpected content. An XML markup fragment is expected.
Empty Attribute Found
Element <epub:default> contains an empty ‘id‘ attribute. The ‘id‘ attribute should have a value when present.
Duplicate Element ID Found
An element’s ‘id‘ attribute must be unique. You have included an ‘id‘ attribute in an element (<NAME>) that contains a duplicate of another element’s ‘id‘ (<ID>).
Unexpected Content Found
Element <epub:default> appears to contain unexpected content. An HTML5-compliant markup fragment is expected.
Switch Format Error
Element <epub:switch> contains no <epub:case> child elements. At least one <epub:case> child element is required.
Switch Format Error
Element <epub:switch> contains no <epub:default> child elements. The last child of the <epub:switch> element must be <epub:default>.
Switch Format Error
Element <epub:switch> contains multiple <epub:default> child elements. Only one <epub:default> element is required.
Obsolete Element Found

(version 3.1)
Element <epub:switch> is not supported in EPUB version 3.1. Consider the MathML ‘altimg‘ attribute guidance for options.
Element Placement Error
Element <NAME> contains an <epub:trigger> child element. The <epub:trigger> should only be used in the <head> element and HTML5 Flow Content.
Empty Attribute Found
Element <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute must have a value.
Unexpected Value Found
Element <epub:trigger> must have a ‘ref‘ attribute that specifies the ‘id‘ of the element that is the object of the action. No elements with a matching ‘id‘ attribute can be found in the resource.
Unexpected Value Found
Element <NAME> contains an ‘<ATTRIBUTE>‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: <LIST>.
Required Attribute Missing
Element <NAME> has no ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute is required.
Empty Attribute Found
Element <NAME> contains an empty ‘<ATTRIBUTE>‘ attribute. The ‘<ATTRIBUTE>‘ attribute should have a value when present.
Obsolete Element Found

(version 3.1)
Element <epub:trigger> is not supported in EPUB version 3.1. Use the native controls provided by the HTML <audio> and <video> elements instead.
EPUB Namespace Error
Element <html> contains an empty ‘xmlns:epub‘ attribute. The ‘xmlns:epub‘ attribute must have a value when the page contains one or more elements or attributes with ‘epub’ prefixes (such as the ‘epub:type‘ attribute or the <epub:switch> element).
EPUB Namespace Error
Element <html> contains an ‘xmlns:epub‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.idpf.org/2007/ops.
EPUB Namespace Error
Element <html> has no ‘xmlns:epub’ attribute. The ‘xmlns:epub‘ attribute is required when the page contains one or more elements or attributes with ‘epub‘ prefixes (such as the ‘epub:type‘ attribute or the <epub:switch> element).
Forbidden Attribute Found
Element <NAME> carries the ‘ssml:ph‘ attribute. Element <NAME> is the descendant of an element that carries the same attribute. This is not allowed.
SSML Namespace Error
Element <html> contains an empty ‘xmlns:ssml‘ attribute. The ‘xmlns:ssml‘ attribute must have a value when the page contains one or more attributes with ‘ssml‘ prefixes (such as ‘ssml:ph‘ or ‘ssml:alphabet‘).
SSML Namespace Error
Element <html> contains an ‘xmlns:ssml‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.w3.org/2001/10/synthesis.
SSML Namespace Error
Element <html> has no ‘xmlns:ssml‘ attribute. The ‘xmlns:ssml‘ attribute is required when the page contains one or more attributes with ‘ssml‘ prefixes (such as ‘ssml:ph‘ or ‘ssml:alphabet‘).
Deprecated Attribute Found
Element <NAME> contains a deprecated attribute (‘aria-describedat‘). Consider removing the attribute or replacing it with something current.
MathML Namespace Error
Element <html> contains an empty ‘xmlns:m‘ attribute. The ‘xmlns:m‘ attribute must have a value when the page contains one or more elements with ‘m:‘ prefixes (such as <m:math> or <m:annotation-xml>).
MathML Namespace Error
Element <NAME> contains an ‘xmlns:m‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.w3.org/1998/Math/MathML.
MathML Namespace Error
Element <html> has no ‘xmlns:m‘ attribute. The ‘xmlns:m‘ attribute is required when the page contains one or more elements with ‘m:‘ prefixes (such as <m:math> or <m:annotation-xml>).
Dimension and Alignment Attributes Recommended
Element <NAME> contains an ‘altimage‘ attribute without the recommended dimension and alignment attributes. Consider adding the following attributes to the element: altimg-width, altimg-height and altimg-valign.
Private Use Area (PUA) Characters Found
The resource contains characters that fall within the Unicode Private Use Area (PUA) ranges. Please ensure that these characters occur within a string that is styled or attributed in a manner that includes a reference to an embedded font that contains an appropriate glyph for that code point.
Discouraged Element Found
Element <rp> is discouraged. EPUB 3 Reading Systems are ruby-aware, and can provide fallbacks for ruby markup.
Discouraged Element Found
Element <embed> is discouraged. Authors should use the object element instead.
Forbidden Element Found
Element <NAME> is a SVG Animation Element. SVG Animation Elements are not allowed.
Forbidden Attribute Found
Element <NAME> includes an SVG Animation Event attribute (‘<ATTRIBUTE>‘). SVG Animation Events are not allowed.
SVG Namespace Error
Element <svg> contains an empty ‘xmlns‘ attribute. The ‘xmlns‘ attribute should have a value when present.
SVG Namespace Error
Element <svg> contains an ‘xmlns‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.w3.org/2000/svg.
SVG Namespace Error
Element <svg> needs a namespace declaration. Specify the ‘xmlns‘ attribute with the value ‘http://www.w3.org/2000/svg‘ on the <svg> element (or one of its parent elements).
Unexpected Content Found
Element <svg:title> contains unexpected content. The <svg:title> element must contain only valid XHTML Phrasing Content.
Unexpected Content Found
Element <svg:foreignobject> contains unexpected content. The <svg:foreignobject> element must contain either valid XHTML Flow Content or a single <body> element.
Unexpected Value Found
Element <svg:foreignobject> contains an ‘requiredextensions‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.idpf.org/2007/ops.
SVG Namespace Error
Element <html> contains an empty ‘xmlns:svg‘ attribute. The ‘xmlns:svg‘ attribute must have a value when the page contains one or more elements with ‘svg:‘ prefixes (such as <svg:title> or <svg:foreignobject>).
SVG Namespace Error
Element <html> contains an ‘xmlns:svg‘ attribute that specifies an unexpected value (<VALUE>). Allowed values are: http://www.w3.org/2000/svg.
SVG Namespace Error
Element <html> has no ‘xmlns:svg‘ attribute. The ‘xmlns:svg‘ attribute is required when the page contains one or more elements with ‘svg:‘ prefixes (such as <svg:title> or <svg:foreignobject>).
Unexpected Value Found
Element <link> appears to reference a PLS Document with an unexpected extension (<EXT>). The PLS Document filename specified in the ‘href‘ attribute should use the file extension ‘.pls‘.
Unexpected Value Found
Element <link> appears to reference a PLS Document, but the ‘type‘ attribute specifies an unexpected value (<VALUE>). The ‘type’ attribute must be set to ‘application/pls+xml‘.
Unexpected Value Found
Element <link> appears to reference a PLS Document, but the ‘rel‘ attribute specifies an unexpected value (<VALUE>). The ‘rel‘ attribute must be set to ‘pronunciation‘.
Required Attribute Missing
Element <link> appears to reference a PLS Document, but the ‘rel‘ attribute is missing. The ‘rel‘ attribute must be set to ‘pronunciation‘.
Recommended Attribute Missing
Element <link> appears to reference a PLS Document, but the ‘hreflang‘ is missing. The ‘hreflang‘ should be set to a RFC5646 language code to match the PLS Document.
Deprecated Element Found

(version 3.2)
Element <NAME> contains an <epub:switch> child element. The <epub:switch> element is deprecated.
Deprecated Element Found

(version 3.2)
Element <NAME> contains an <epub:trigger> child element. The <epub:trigger> element is deprecated.

CSS

Checks EPUB-specific declarations and properties.

TitleTypeMessage
Absolute Positioning without Pre-pagination
The ‘absolute‘ value of the ‘position‘ property should be used only with XHTML Content Documents whose ‘rendition:layout‘ property is set to ‘pre-paginated‘. No references to this resource could be found in the <spine> element of an OPF listed in container.xml.
Absolute Positioning without Pre-pagination
The ‘absolute‘ value of the ‘position‘ property should be used only with XHTML Content Documents whose ‘rendition:layout‘ property is set to ‘pre-paginated‘. This resource is not pre-paginated according to its corresponding <itemref> properties (<VALUES>) in the <spine> element of the OPF named: <FILENAME>.
Absolute Positioning without Pre-pagination
The ‘absolute‘ value of the ‘position‘ property should be used only with XHTML Content Documents whose ‘rendition:layout‘ property is set to ‘pre-paginated‘. This resource is not pre-paginated according to the global ‘rendition:layout‘ property (<VALUES>) in the <metadata> element of the OPF named: <FILENAME>.
Absolute Positioning without Pre-pagination
The ‘absolute‘ value of the ‘position‘ property should be used only with XHTML Content Documents whose ‘rendition:layout‘ property is set to ‘pre-paginated‘. This resource is not pre-paginated according to the combined effect of the global ‘rendition:layout‘ property (<VALUES-A>) in <metadata> and its corresponding <itemref> properties (<VALUES-B>) in the <spine> element of the OPF named: <FILENAME>.
Fixed Positioning Found
CSS ‘position‘ property specifies the ‘fixed‘ value. The ‘fixed‘ value is not part of the EPUB 3 CSS Profile. To avoid potential rendering and interoperability issues, it should not be included in an EPUB Style Sheet.
Direction Property Found
CSS ‘direction‘ property must not be included in an EPUB Style Sheet. Authors should use appropriate [HTML5] markup to express directionality information instead.
Unicode-BIDI Property Found
CSS ‘unicode-bidi‘ property must not be included in an EPUB Style Sheet. Authors should use appropriate [HTML5] markup to express directionality information instead.
An -EPUB-Prefixed Version of the Property is Available
CSS ‘<NAME>‘ property was detected. The EPUB 3 CSS Profile contains an ‘-epub-‘ prefixed version of this property. Consider using ‘<PROPERTY>‘ instead.
Unsupported Property Found

(versions 3.1 and 3.2)
CSS ‘<NAME>‘ property was detected. This property is not supprted in EPUB version <VERSION>.
Unsupported Value Found
CSS ‘-epub-hyphens‘ property specifies the ‘all‘ value. The ‘all‘ value is not supported.
Deprecated Value Found

(version 3.0.1)
CSS ‘-epub-text-orientation‘ property uses one or more of the following deprecated values: ‘vertical-right‘, ‘rotate-right‘, ‘rotate-left‘, ‘rotate-normal‘ and ‘auto‘. Consider using one of the following instead: ‘mixed‘, ‘sideways-right‘, ‘sideways-left‘, ‘sideways‘ and ‘use-glyph-orientation‘.
Unsupported Value Found

(versions 3.1 and 3.2)
CSS ‘-epub-text-orientation‘ property uses one or more unsupported values. Consider using one of the following instead: ‘upright‘, ‘mixed‘, ‘sideways-right‘ and ‘sideways‘.
Deprecated Property Found
CSS ‘-epub-text-combine‘ property is deprecated. Consider using ‘-epub-text-combine-horizontal‘ instead.
Deprecated Value Found
CSS ‘display‘ property specifies a deprecated value (oeb-page-head). Consider changing the value.
Deprecated Value Found
CSS ‘display‘ property specifies a deprecated value (oeb-page-foot). Consider changing the value.
-EPUB-Prefixed Property Found

(version 3.1)
One or more CSS properties with the ‘-epub‘ prefix were detected. In EPUB version 3.1, authors are strongly encouraged to use unprefixed properties from CSS-native solutions instead.
-EPUB-Prefixed CSS Speech Property Found

(version 3.2)
One or more CSS Speech properties with the ‘-epub‘ prefix were detected. These properties are not supported in EPUB version 3.2.

Images

Checks for images that are larger than 2.5 MB.

TitleTypeMessage
Large Image FoundImage at path ‘<PATH>‘ is large (<SIZE>). Consider replacing the image with a smaller or more compressed version of itself.