EPUB · PDF · MOBI · DOCX · Markdown
Free E-book Tools
Convert, edit, validate, compress, and prepare EPUB, PDF, MOBI, AZW3, DOCX, HTML, TXT, and Markdown files for Kindle, Apple Books, Kobo, publishing, and study. Browser tools run locally — no upload, no account.
Available now in your browser
These tools run entirely in your browser using your files. No upload, no account required.
EPUB Inspector
Inspect EPUB internals: metadata, file tree, manifest, spine, table of contents, images, and CSS files.
Metadata Editor
Edit EPUB metadata: title, author, publisher, language, description, date, rights, and subject. Download the updated EPUB.
EPUB Validator
Check EPUB structure for common errors: missing files, broken metadata, invalid OPF, missing cover, and broken internal links.
Add Cover
Add or replace the cover image in an EPUB file. Supports JPG, PNG, and WebP. Download the updated EPUB.
EPUB to PDF
Convert an EPUB e-book to PDF. Choose page size, font, margins, and whether to include the cover and table of contents.
Compress EPUB
Reduce EPUB file size by re-compressing all assets with maximum compression. See before and after file sizes.
Kindle Checker
Check whether your EPUB is ready for Kindle upload. Verifies cover, metadata, TOC, file size, images, and common Kindle issues.
Word Count
Count words, characters, and chapters in an EPUB, DOCX, TXT, or Markdown file. See word count per chapter.
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, add covers, fix table of contents, and clean EPUB files
Export
Export from EPUB
Export EPUB content to PDF, TXT, Markdown, and other formats
Optimize
Compress & Optimize
Reduce EPUB and PDF file sizes, compress images, and remove unused assets
Split / Merge
Split & Merge
Split EPUB files by chapters or merge multiple EPUB files into one book
Extract
Extract Content
Extract text, images, chapters, and outlines from EPUB and PDF files
Study
Study & Reading
Word count, reading time, chapter outlines, and study-friendly text exports
Publishing
Author & Publisher
Publishing checklists, metadata helpers, cover tools, and delivery packages
Your e-book files, handled privately
Tools labeled Browser process your files entirely in your browser — your files never leave your device. Tools labeled Server send files for processing only for the selected operation and delete them after. 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 support EPUB, TXT, and Markdown in your browser. Other e-book formats such as DOCX, RTF, MOBI, and AZW3 are not handled here — convert them in a dedicated reader 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?
Start with the EPUB Inspector to review your file, then use the Kindle EPUB Checker to identify any issues. Fix metadata with the EPUB Metadata Editor, ensure your cover image meets Kindle's size requirements, and compress the EPUB if it is too large.
Why does PDF to EPUB conversion change formatting?
PDF files are designed as fixed pages. EPUB files are designed to reflow text across different screen sizes. During conversion, headings, paragraphs, images, tables, and page breaks may need to be rebuilt — complex PDFs may not convert perfectly.