Write and publish EPUBs with ease

Steelkilt is a powerful writing app that lets you create amazing EPUBs.

Every facet of the publishing process is covered. Structure your work easily. Produce high-quality writing with a distraction-free editor. Remove inconsistencies with powerful search capabilities. Annotate and export to a range of file formats. Generate your EPUB automatically. Effortlessly customize your EPUB’s XHTML. Let the app check your EPUB’s formatting and fix EPUB problems for you.

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Write like you are reading

Steelkilt’s distraction-free text editor allows the author to step into the reader’s shoes during the creative process with preconfigured font and paper-color options that are designed to maximize readability and writing comfort in both bright and low-light environments.

Powerful text processing

Use Markdown directives or HTML tags to enhance the appearance of your work. Steelkilt will accurately process your mix of text, Markdown and HTML when exporting to EPUB (or any of the other available formats).

Easily embed images and create links

Use drag and drop to embed images and create links with zero effort.* Behind the scenes, Steelkilt will convert these additions to your text to HTML and help to ensure that all links are valid.

Get help with tags and linkable resources

When Steelkilt thinks that you are about to type an HTML tag, or a Markdown link or image directive, it will display an autocompletion menu with a collection of context-specific suggestions for your convenience.

Stay organized

Use keywords and color-coded tags to organize your work. Both are searchable.

Monitor your progress

Steelkilt collects statistics as you write. Select a book, part or chapter to view its available metrics.


Structure your work like a book

Steelkilt’s project navigator allows authors to structure their work like a book. Quickly create front and back matter, chapters and parts. When your EPUB is compiled, this structure will automatically become the table of contents.

Build the sections of your book as you write or import collections of documents from elsewhere. Easily restructure your book with drag and drop. If your book becomes very large, create a new part from a selection of chapters.

Enhance your title pages with images

Give your book a cover image. If your book has parts, optionally include an image on the part’s title page.

Easily manage your table of contents inclusions

Steelkilt automatically includes all body matter in the table of contents, and excludes front and back matter. Overriding these settings and changing document types is easy.

Customize the formatting of your table of contents and page titles

Steelkilt automatically manages part and chapter numbering. You can choose how numbering appears in page titles and table of contents entries. Use words, numbers or roman numerals — or use no numbering at all.


Find what you need

Steelkilt includes a powerful search engine that allows an author to find text, keywords and tags. Look for text that contains a word or matches a pattern (such as a wildcard phrase or regular expression). Search your book’s text or your EPUB’s code. You can limit the scope of your search as required.

Review what you have found

Steelkilt displays lines matching your search criteria in a preview that includes highlighting. Click on a search result to open the relevant document for editing. If you change your content, search results are updated in real time.

Replace with confidence

You can replace one search result or replace them all. If you make a mistake, Steelkilt supports undo.

Narrow your focus

Steelkilt provides a range of filters to help you stay focused. Filter books, parts and chapters by name. Filter annotations by the content of the annotated text or your notes. Refine searches even further with search result filters. Filter resources in the code editor by file name.


Annotate like a professional

Steelkilt allows authors and editors to annotate text in the project with underlining and a range of highlight colors. Notes can be added to the annotations. Annotations can be merged. If an author finds annotations distracting, they can hide annotations from view.

Manage your annotations with ease

All annotations in your Steelkilt project are listed in a dedicated view that shows the date/time when the annotation was created, the annotation type, the annotated text and notes. Jump from annotations to the annotated text. If you change the annotated text, the annotation list will be updated in real time.


Awesome EPUB generation

Steelkilt builds a preview of your EPUB as you write. The preview reflects your selected EPUB version. Everything in the preview is generated automatically — and a complete, nicely formatted EPUB can be exported from the preview without changing any default options or writing any XHTML code. But for those authors and digital publishers who want to customize their EPUBs, Steelkilt includes a built-in code editor. Using the code editor, you can browse and customize the XHTML that will make up your EPUB at any time before export.

No customization limits

Hack the automatically generated XHTML. Change EPUB formatting and appearance by tweaking CSS. Import files to create non-XHTML renditions. Add documents to your container (such as encryption.xml etc.)

Edit code like a programmer

The code editor includes all the features you would expect to find in a professional code editor: line numbering, syntax highlighting, code autocompletion, themes, commands for indenting and bulk commenting.

Lock, regenerate and restore

Editing a generated file will lock it, such that it is excluded from subsequent regenerations. Unlock the file and Steelkilt will undo your customizations. Trigger XHTML regeneration manually. Restore templates and default CSS to their default.

Own your EPUB structure

The inspector for all non-custom items in the preview (such as templates and automatically generated XHTML resources) includes some information explaining the purpose of the selected item and tips for its use.


Intelligent EPUB error handling

Steelkilt includes a powerful built-in EPUB checker that is capable of detecting hundreds of different EPUB, XHTML and CSS problems. Problem checks are EPUB-version specific. You can run the checker at any time. Problems are classified as errors and warnings, the source of the problem is identified and the nature of the problem is fully described.

More than just checking

Clicking on an EPUB content problem will take you to the affected resource or setting.** If the problem is located in some XHTML or CSS code, the problem is highlighted. Further, Steelkilt will display a popover that supplements the problem details with options for fixing the problem. In many cases, Steelkilt will ask you to provide information that it needs to fix the problem (by typing values for missing attributes or choosing from a list of available options). Sometimes, Steelkilt will be able to fix the problem with a click of a button.


Flexible export options

Steelkilt can export your work to EPUB (versions 3.01, 3.1 and 3.2), PDF, RTFD, plain text and HTML. Export your whole book or a specific chapter. A range of options is available for each export type, such as table of contents inclusion and stripping Markdown/HTML.

Export annotations in PDF

Annotations can be included in PDF exports. The PDF annotations’ colors, positioning and notes will mirror the annotations made in Steelkilt.



Support for some features varies between Steelkilt for macOS and Steelkilt for iOS/iPadOS:

* Use Steelkilt’s Link Tool and Image Tool in iOS and iPadOS to add links and images to your text and code, rather than drag and drop

Some features, such as autocompletion menu, filters, bulk-restructuring commands, and HTML exports are only available on macOS

On iOS and iPadOS, only keyword highlighting and themes are supported in Code Editor

** On iOS and iPadOS, the workflow for dealing with EPUB content problems is slightly different to macOS.

For more information, read:

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