EPUB · PDF · TXT · Markdown
E-book Tools
Check, edit, compress, split, and merge EPUB files, check them against Kindle, Apple Books, and Kobo's published rules, and export them as PDF, TXT, or Markdown for publishing and study. Open a tool and start; your files are processed on your device.
Available now in your browser
These tools run entirely in your browser using your files; your data stays on your device.
EPUB Inspector
See what is inside an EPUB: metadata, table of contents, reading order, stylesheets, and every file by size.
Metadata Editor
Edit EPUB metadata: title, author, publisher, language, description, date, rights, and subjects. Download the updated EPUB.
EPUB Validator
Check an EPUB for the structural errors that most often block a book: mimetype, identifier, manifest, spine, table of contents, malformed XHTML, missing files.
Add Cover
Add or replace the cover image in an EPUB. JPG, PNG or WebP in; a cover page is added when the book has none. Download the updated EPUB.
EPUB to PDF
Convert an EPUB's text to PDF. Choose the page size, font size and margins, with an optional table of contents and a title page from the metadata.
Compress EPUB
Make an EPUB smaller: re-pack every file with maximum compression, drop system junk, and optionally re-encode JPEG photos. See the before and after sizes.
Kindle Checker
Check an EPUB against Amazon KDP's published rules: the cover inside the book, the EPUB structure and metadata, plus what the file size costs on KDP.
Word Count
Count words, characters and chapters in an EPUB, TXT or Markdown file, with a per-chapter word count for EPUBs and an estimated page count.
Inspect
Inspect & Analyze
Explore EPUB internals, metadata, file structure, and content stats
Validate
Validate & Check
Validate EPUB structure and check readiness for Kindle, Apple Books, and Kobo
Edit
Edit & Fix
Edit EPUB metadata and add or replace the cover
Export
Export from EPUB
Export EPUB content to PDF, TXT, and Markdown
Optimize
Compress & Optimize
Re-pack an EPUB with maximum compression and optionally re-encode JPEG photos
Split / Merge
Split & Merge
Split EPUB files by chapters or merge multiple EPUB files into one book
Extract
Extract Content
Extract the text and images from EPUB files
Study
Study & Reading
Word count, reading time, chapter outlines, and study-friendly text exports
Publishing
Author & Publisher
Package a finished EPUB with its cover, metadata and a Kindle pre-check for delivery
Your e-book files, handled privately
Every tool on this page processes your files in your browser, so your files stay on your device. We do not remove DRM, bypass copyright protection, or claim ownership of your files.
Only upload e-books and documents you own or have permission to process. Do not upload DRM-protected commercial books.
Frequently asked questions
Can these tools remove DRM from e-books?
No. These tools cannot remove DRM or bypass copyright protection. Only use files you own, have purchased DRM-free, or have permission to process.
What formats are supported?
The tools on this page open EPUB files, and the word count and reading time tools also read TXT and Markdown. Results can be exported as PDF, TXT, Markdown, CSV, JSON, or ZIP, depending on the tool. Other e-book formats such as DOCX, RTF, MOBI, and AZW3 are not handled here: convert them to EPUB in a dedicated app before using FormatOS.
Is EPUB better than PDF for e-books?
EPUB is a reflowable format that adapts to any screen size: ideal for e-readers, phones, and tablets. PDF is a fixed-layout format, ideal for printing and documents with precise layout requirements. Most e-reading apps prefer EPUB.
How do I prepare an EPUB for Kindle?
Run the Kindle EPUB Checker, which applies the rules KDP publishes: a cover inside the book at least 1200 pixels in width or height, a sound EPUB structure, and a title and language. Fix metadata with the EPUB Metadata Editor and the cover with Add Cover to EPUB. KDP sets no maximum EPUB size, but on the 70% royalty option it charges a delivery cost per megabyte, so compressing a large book can pay. Preview the result in Amazon's Kindle Previewer before publishing.
Do the store checkers guarantee my book will be accepted?
No. They apply the rules each store publishes, read from the store's own help pages and linked in every report, plus the EPUB structure checks. Stores run their own validation during upload and can raise issues these checks do not cover.