Convert EPUB to MOBI
Before converting anything, check the year on your Kindle. Since 2022, Amazon has accepted EPUB through Send to Kindle and stopped accepting MOBI, which reverses the advice most pages about this still give. MOBI is for hardware that predates that change.
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Up to 50 MB. Deleted automatically after 30 minutes.
What it does
- Chapters, table of contents and metadata carried across
- Cover image preserved as the book's cover
- Text re-flows on the device, as an e-book should
- No watermark and no sign-up
How to use EPUB to MOBI
- 1
Add the EPUB
A book from a public-domain library, a DRM-free store, or a document you exported as EPUB yourself. Files with DRM cannot be converted, here or anywhere else.
- 2
Convert
A full e-book toolchain runs on our server, parsing the EPUB's structure and rebuilding it as MOBI. Large books with many images can take tens of seconds.
- 3
Get it onto the Kindle
Copy the file to the device's documents folder over USB. Email delivery is the other route, though Amazon's service no longer takes MOBI, so USB is the dependable one for this format.
How it works
The EPUB is unpacked, its spine and navigation document are read to establish chapter order, and the content is rebuilt as a MOBI database with its own indexes for text, table of contents and images.
The conversion is structural rather than visual. An e-book has no fixed pages — the reader decides where the lines break based on font size and screen width — so what actually transfers is the hierarchy of the book and the markup of its text, not any particular arrangement of it.
What survives, and what does not
Survives: chapter divisions, reading order, the navigable table of contents, italics and bold, block quotes, footnote links, images, and metadata like title and author.
Degrades: stylesheets. MOBI predates the CSS that most EPUBs rely on, and its renderer silently ignores what it does not understand. Careful typography becomes plain paragraphs.
Disappears: embedded fonts, fixed-layout pages, SVG illustrations, audio and video, and anything driven by JavaScript. Fixed-layout books — comics, children's picture books, anything where art and text are positioned together — should not be converted to MOBI at all. The format has no way to express them.
The DRM question
A book bought from most stores carries encryption tied to an account, and a converter cannot read it. The failure is usually silent and confusing: the file appears to convert and the output is unreadable or empty, because what was processed was the encrypted payload rather than the book.
If a file behaves that way, DRM is the likely explanation. Buying DRM-free editions, or using a library that distributes them, is the route that does not end in this problem.
Choosing a target format
For a Kindle from roughly 2016 onward, send the EPUB directly and skip conversion entirely.
For an older device that reads AZW3, convert to AZW3 — same lineage, much better typography, and no real downside.
Reach for MOBI when the device is old enough that it is the only thing that loads, or when a tool in your workflow specifically demands it. It is the most compatible format in this family and the least capable, and those two facts are the same fact.
Examples
A public-domain novel
Slightly larger, which surprises people. MOBI stores its own index structures alongside the text and compresses less aggressively than the ZIP an EPUB is built on, so a plain-text-heavy book usually grows a little in translation.
An illustrated technical book
The figures survive; the styling largely does not. MOBI's rendering is built on a much older subset of HTML, so multi-column layouts, precise spacing and anything depending on modern CSS collapse into a single readable column. For a book like this, AZW3 is the better target.
Frequently asked questions
Do I actually need MOBI?
Probably not, if your Kindle is recent. Amazon added EPUB support to Send to Kindle in 2022 and dropped MOBI from that service at the same time, so for current devices you can email or upload the EPUB unchanged. Converting is for older hardware, or for sideloading over USB to a device that never received newer firmware.
What is the difference between MOBI and AZW3?
They are two generations of the same lineage, distinguishable by a version number in the file header: 6 for MOBI, 8 for AZW3. AZW3 understands far more modern formatting — real CSS, embedded fonts, better typography — while MOBI's renderer dates from the mid-2000s. If your device supports AZW3, prefer it.
Will my highlights and notes come across?
No. Annotations live in the device's own storage keyed to a specific book file, not inside the book, so a converted copy arrives as a new title with nothing attached. Your existing notes stay with the existing file, which is a good reason to keep it rather than delete it after converting.
Why did my book arrive with no cover?
Usually because the EPUB marked its cover image ambiguously. The format allows a cover to be declared in more than one place, and files exported by word processors frequently declare it in none — the image is simply the first page. Setting the cover explicitly in an e-book editor before converting fixes it permanently.