Merge EPUB Files for Free

The Epublys merge tool is free. No account, no watermarks, no export paywalls. Upload, order, merge, download. Here's exactly what the free tier includes and what you should know before using it.

Free Tier Limits

• Up to 10 EPUB files per merge
• Up to 10MB per file
• Unlimited merges — no daily caps
• No account or email required
• Files processed in memory on a Cloudflare Worker, never written to disk
• SSL-encrypted transfer

Most text-heavy EPUBs are well under 10MB. Image-heavy books (photography, comics, illustrated textbooks) are the exception — for those, Pro supports up to 500 files at 100MB each. The 10MB cap is per individual file; if your file is larger, compress it first — most image-heavy EPUBs drop well under 10MB after optimization.

How to Merge EPUB Files for Free

1. Open the Merge EPUB tool
2. Add up to 10 files by dragging or clicking to browse. Drag-drop ordering and previews stay in your browser; the merge itself runs in-memory on a Cloudflare Worker over HTTPS — files are never written to disk.
3. Drag the file cards into the order you want — first card becomes the first section of the merged book
4. Click Merge EPUBs — takes a few seconds regardless of file count
5. Download your merged EPUB

What Happens to Metadata, CSS, and TOC

Metadata: Inherited from the first file in the merge order. If that file's title and author are correct, the merged result will be too. If not, the metadata editor takes about 30 seconds to fix — update title, author, and cover without re-merging.

CSS stylesheets: Each source file's stylesheets are preserved and namespaced so they don't collide. Two books with body { font-family: Georgia; } won't fight. If you see visual inconsistency between sections (different default fonts or spacing), the source books have genuinely different stylesheets — strip and reapply a single stylesheet in Sigil if consistency matters.

Table of contents: All source TOC entries are assembled in spine order. If a source file had a well-structured NAV document, its chapter entries appear under a heading for that book. If a source had no TOC, its content is included in the correct order but without named chapter entries. For academic use or distribution, check the merged TOC in a reader before publishing.

Images and fonts: Image files from each source are bundled into the merged output. Duplicate filenames (two books with a cover.jpg) are automatically renamed to prevent collisions — neither breaks. Font files are deduplicated: if two books embed the same font, only one copy ends up in the merged file.

Common Use Cases

Author series into a single omnibus

Self-published authors frequently bundle a completed trilogy or series into a single omnibus EPUB for sale at a discount. Drop all three books in, order them by publication order, merge. Then update the title to "Series Name Omnibus" and set the cover to the omnibus design using the metadata editor. Validate before uploading to KDP — merged files occasionally produce duplicate ID errors that Apple Books rejects even when Calibre opens them fine.

Librarian managing donated ebook collections

If you receive EPUB donations in separate volumes and want to archive them as a single file, merge is the right approach. The structure-preserving behavior of the TOC merge means each original book's chapter markers stay intact. Run the validator after merging to confirm the output meets epubcheck standards before archiving.

Researcher combining report sections

Research teams exporting to EPUB from Google Docs or Pandoc sometimes produce one file per section. Merging gives you a single navigable document. Note: if the individual files don't have consistent heading structures, the combined TOC will be flat rather than hierarchical. Edit in Sigil post-merge if a nested structure matters.

Reader extracting sample chapters first

If you used the splitter to pull specific chapters out of multiple books, merge reassembles your custom selection into one file. Drop the extracted chapter EPUBs in, order them, merge. The result is a reading list in a single navigable file.

What Goes Wrong (and How to Fix It)

Validation fails after merge — most common cause is duplicate element IDs. Books often reuse IDs like chapter-1 or toc, which must be unique across the combined file. Epublys deduplicates these automatically, but if you merges files that were pre-processed by other tools, duplicates can slip through. Fix with the validator's auto-fix.

Cover image from the wrong book — metadata inherits from the first book in the order. If the cover in your merged file is from book two, re-order the cards so book one is first, then re-merge. Or update the cover directly in the metadata editor without re-merging.

Output is too large — multiple books means multiple cover images, and cover images are often unoptimized. A merged file from three illustrated books could be 25MB when each source was 8MB. Run it through the EPUB compressor after merging — covers alone account for 30–50% of typical bloat.

Chapters look inconsistent — this is the source books having different CSS, not a bug. The merger preserves each book's stylesheet. If you want visual consistency across the merged result, you'll need to open it in Sigil, delete the extra stylesheets, and apply a single unified CSS file.

Calibre's Merge vs Epublys Merge

Calibre has a "Merge selected records" function. It works, but it's primarily designed as a library deduplication tool — it merges metadata records and concatenates content. The content combining is less careful about preserving TOC structure and namespacing CSS than a purpose-built merge tool. For files already in your Calibre library, it's convenient. For everything else, the browser merge is faster and doesn't require an install. See the full Calibre comparison.

After Merging: Three Steps

1. Validate the merged file — merging is one of the more reliable ways to introduce structural errors, particularly duplicate IDs
2. Fix the metadata — update the title, author, and cover for the combined work
3. Compress if the output is large — multiple books' cover images stack up fast

• How to merge EPUB files — all methods including Calibre and command line
• Compress your merged EPUB
• Edit metadata on your merged file
• How to create an EPUB from scratch