Sigil
Sigil is an open-source editor for creating and refining EPUB books with structured text, styles, metadata and a navigable table of contents. This page covers EPUB structure, validation, images and accessible export habits.
What Sigil provides
Sigil edits the structured contents of an EPUB, including chapter XHTML, stylesheets, images, metadata and navigation. It is suited to a controlled publishing workflow, but it does not replace a full editorial review or verify that a book's content and embedded assets are licensed.
Structure and validation
Keep chapter headings consistent, use styles rather than repeated inline formatting and maintain a meaningful reading order. Add metadata early, rebuild the table of contents after structural changes and validate the package before sharing it. Keep the source manuscript and image assets in a separate versioned folder.
Maintenance note
This page reviews Sigil for EPUB chapter editing, styles, metadata, navigation and package validation. Content review date: 2026-08-23.
Save to your cloud drive
Open the cloud drive to get the file directly, or save it for convenient access on another device.
Quark Cloud Drive
RecommendedSave Sigil to this cloud drive
Baidu Netdisk
Save Sigil to this cloud drive
Sigil EPUB editing and validation guide
Open a copy of a small EPUB, inspect its structure, edit one chapter and stylesheet, rebuild navigation and validate the result before publishing.
Before you start
- Prepare a source manuscript, licensed images and a backup copy of the original EPUB.
- Decide the chapter hierarchy and metadata fields required by the target reader.
- Keep a separate folder for source text, images, fonts and exported packages.
Installation steps
- 01
Install and open a working copy
Install Sigil, open a copied EPUB and inspect the book browser, chapter files, stylesheet and metadata before editing.
- 02
Edit a chapter and style
Change one heading and paragraph, use the stylesheet for visual rules and preview the result in a reader-like view.
- 03
Rebuild navigation and validate
Generate or refresh the table of contents, check reading order and run the EPUB validator before saving a new version.
Quick start
- 01
Normalize headings
Use a consistent heading hierarchy, keep one main title per chapter and avoid styling a heading only through manual font changes.
- 02
Review metadata and cover
Check title, author, language, identifier and cover details, then confirm that embedded assets have the expected dimensions and names.
- 03
Test in a second reader
Open the exported package in another reader, inspect links and page turns and record any device-specific rendering difference.
Usage tips
- Keep source files and generated EPUB packages separate so a later export can be compared with the previous version.
- Fonts, images and quoted content need their own license and distribution review.
- Re-run validation after changing filenames, navigation or package metadata.
Troubleshooting and uninstall
Why is a chapter missing from the table of contents?
Check the heading level and document structure, rebuild navigation and inspect the generated navigation file before testing again.
Why does the EPUB look different in another reader?
Compare stylesheet support, font availability, image dimensions and viewport behavior. Keep the markup simple and test a short chapter before changing every style.
- Archive the source and packageSave the source manuscript, assets, validation result and final EPUB in a versioned folder that can be reopened.
- Remove the editorUninstall Sigil through the operating system and remove caches only after confirming that the source and generated package are independent.
Frequently asked questions
Does Sigil replace editorial proofreading?
No. It edits EPUB structure and presentation; language, accessibility, copyright and final reading checks remain part of the publishing workflow.
When should an EPUB be validated?
Validate after structural edits and again before distribution, especially after changing navigation, filenames, metadata or embedded assets.
Does the download require an extraction code?
The Quark entry does not require one; the four-character code for the Baidu entry is shown beside its download entry.