EPUB to MOBI converter

MOBI is a legacy Kindle format; Amazon Send-to-Kindle has accepted EPUB since 2022, so convert only for older devices or fixed workflows.

Converted with Ebook engine · input deleted within 24 h
Free: 5 conversions a day · 5 MB each
Higher limits →

From real runs

What you get — and what changes

Element	Result	What happens
MOBI target model	Changed	Our ebook engine writes a legacy Kindle package, so modern EPUB structure is simplified to what older Kindle software understands.
KF8 and fixed layout features	Lost	Fixed-layout pages, rich CSS, media overlays, SVG-heavy layouts, and some EPUB 3 semantics are dropped or flattened.
Text and chapters	Kept	Main body text, headings, chapter order, and basic table of contents entries normally survive.
Cover thumbnail	Changed	Kindle libraries show a thumbnail only when cover metadata is valid and the receiving device or app rebuilds its catalog cache.
CSS	Changed	Basic bold, italic, headings, indents, and paragraph spacing survive; floats, columns, custom fonts, and advanced selectors do not.
Images	Changed	Images are resized and re-encoded for MOBI constraints, which can soften screenshots and diagrams.
Metadata	Kept	Title, author, language, and publisher fields are kept when present, but store-specific ASIN behavior is not recreated.

MOBI target model Changed
Our ebook engine writes a legacy Kindle package, so modern EPUB structure is simplified to what older Kindle software understands.
KF8 and fixed layout features Lost
Fixed-layout pages, rich CSS, media overlays, SVG-heavy layouts, and some EPUB 3 semantics are dropped or flattened.
Text and chapters Kept
Main body text, headings, chapter order, and basic table of contents entries normally survive.
Cover thumbnail Changed
Kindle libraries show a thumbnail only when cover metadata is valid and the receiving device or app rebuilds its catalog cache.
CSS Changed
Basic bold, italic, headings, indents, and paragraph spacing survive; floats, columns, custom fonts, and advanced selectors do not.
Images Changed
Images are resized and re-encoded for MOBI constraints, which can soften screenshots and diagrams.
Metadata Kept
Title, author, language, and publisher fields are kept when present, but store-specific ASIN behavior is not recreated.

Sample conversions

Public-domain novel for Kindle Keyboard

Input: 620 KB EPUB 2 with 28 chapters, cover art, NCX TOC, italicized letters, and simple scene-break ornaments.
Output: 910 KB MOBI opened on an older Kindle app, chapters navigable, italics kept, ornaments became centered text, cover thumbnail appeared after library refresh.

Illustrated EPUB 3 guide

Input: 12 MB EPUB 3 with CSS grid callouts, high-resolution PNG screenshots, SVG icons, and semantic aside elements.
Output: 6.4 MB MOBI, reading order intact, screenshots downsampled, asides converted to ordinary paragraphs, SVG icons rasterized or omitted depending on page.

A real EPUB → MOBI run

We converted our EPUB sample (5 KB) with Ebook engine on 2026-09-11. It took 346 ms and produced a 11 KB MOBI file, 1.9× larger than the input. The engine raised no warnings.

Input · sample.epub · 5 KB

EPUB 3.0: 3 content documents, 0 images, EPUB 3 nav, no cover

Version: 3.0
Content documents: 3
Images: 0
Table of contents: EPUB 3 nav
Cover: no cover

Output · sample.mobi · 11 KB

Palm database, BOOKMOBI (KF7), title “Unknown”

Identifier: BOOKMOBI
Title: Unknown

Options and when to change them

mobiFileType: Use old MOBI only for very old Kindles; prefer AZW3 or EPUB when the receiving workflow supports it.
cover: Set or replace a cover when Kindle library thumbnails matter, because MOBI thumbnails depend on valid cover metadata.
metadata: Normalize title and author before conversion so older Kindle libraries sort the book correctly.

Do it yourself

Calibre ebook-convert

bash

ebook-convert in.epub out.mobi

Prefer sending the original EPUB to modern Amazon Send-to-Kindle unless an older device or internal process specifically requires MOBI.

EPUB to MOBI by API or MCP

The HTTP API and the MCP server run the exact engine this page uses (Ebook engine); the response carries the same warnings the web converter shows. Check support first with GET /api/v1/pairs?from=epub&to=mobi.

curl

curl -X POST https://filetypeconverters.com/api/v1/convert \
  -H "Authorization: Bearer $FTC_API_KEY" \
  -F "file=@input.epub" -F "from=epub" -F "to=mobi" \
  --output output.mobi

API reference

When this is the wrong conversion

Do not convert to MOBI just because the destination is Kindle; Send-to-Kindle accepts EPUB and often gives a better result now.
Use AZW3 rather than MOBI when you need newer Kindle CSS and better image handling on sideloaded files.
Use PDF when the source is fixed-layout and every page must look exactly like the original.

EPUB to MOBI questions

Should I still convert EPUB to MOBI for Kindle?

Usually no. Since 2022, Amazon Send-to-Kindle accepts EPUB. MOBI is mainly for older Kindles, legacy archives, or systems that only ingest MOBI.

Why did my cover not show in the Kindle library?

The MOBI may contain the cover, but Kindle thumbnails depend on metadata, device indexing, and catalog cache refresh. Opening the book once can help.

Does EPUB 3 fixed layout survive as MOBI?

No. MOBI is reflow-oriented and old; fixed-layout and many KF8-era layout features are flattened or lost.