How to Send EPUB to Kindle: Email, App, Limits and Fixes

For fifteen years the Kindle and EPUB did not mix. Amazon built its readers around MOBI, the format it acquired with Mobipocket in 2005, and later around KF8 (AZW3) and KFX, while nearly every other store and library sold EPUB. Getting a book from Kobo, a publisher's site or Project Gutenberg onto a Kindle meant converting it first, usually to MOBI, and emailing that file. In 2022 Amazon reversed the arrangement. Send to Kindle started accepting EPUB attachments, and by the end of that year it stopped accepting MOBI uploads altogether, recommending EPUB for personal documents instead.

The important detail is where the conversion now happens. When you send an EPUB, Amazon's servers rebuild it in a Kindle format before it reaches your device, so the Kindle never sees the EPUB itself. That is why the same file behaves differently depending on how you move it. Through Send to Kindle it arrives as a normal book with chapters, a cover and synced reading position. Copied over a USB cable into the documents folder, it either does not appear in the library at all or shows up as an item the Kindle cannot open.

Nothing changed on the device side. Kindle e-readers still open AZW3, MOBI, KFX, PDF and plain text locally, and none of them gained an EPUB reader in a firmware update. Old MOBI files you sent before the change stay in your library and keep syncing.

All five routes end in the same place: the Docs section of your Amazon library, synced to every Kindle e-reader and Kindle app on the account. Email is the oldest and still the most flexible. Every Kindle and Kindle app gets its own address ending in @kindle.com, listed under Manage Your Content and Devices, then Preferences, then Personal Document Settings. Amazon only accepts mail from addresses on the Approved Personal Document E-mail List on that same page, so add the address you will send from before the first attempt, or the message is silently discarded.

The other routes skip the approved-sender step because you are already signed in. The web uploader at amazon.com/sendtokindle takes a drag and drop from any browser. The desktop app for Windows and macOS adds a right-click entry and a print-to-Kindle option. On a phone, the Kindle app appears in the iOS and Android share sheet, so an EPUB in Files, a download folder or a mail attachment is two taps away. The Chrome extension is the odd one out: it sends web articles, not files.

Pick by where the file already is. A book in your downloads folder goes fastest through the web uploader; a file a friend mailed you goes faster by forwarding it to your Kindle address from an approved account.

Amazon publishes two size ceilings, and which one applies depends on the route. Email caps the message at 50 MB, and that figure covers all attachments together, not each one. The web uploader, the desktop app and the mobile apps take files up to 200 MB. A typical novel EPUB weighs between 0.5 and 5 MB, so neither limit matters for text; illustrated cookbooks, art books and comics are where you hit them. Amazon has also said personal documents share a cloud allowance of 5 GB per account, which is plenty for text but fills up with large comics.

Count limits are less clearly documented. Email accepts up to 25 attachments per message, and the web uploader has historically accepted a similar batch at once; if a larger batch stalls, split it. Delivery is usually a few minutes, but a large or image-heavy file can take longer while the conversion runs.

An EPUB is a ZIP package of XHTML chapters, a stylesheet, images and a manifest that lists them, the same container idea explained in our comparison of ZIP, RAR and 7z. Amazon's converter reads that package and rebuilds it. A well-formed, reflowable novel comes through intact: chapters, headings, italics, footnote links, inline images and the navigation that feeds the Kindle's Go To menu. Trouble starts when the EPUB depends on things the Kindle's layout engine handles differently or not at all.

Fixed-layout EPUBs are the most common casualty. Picture books, comics, manga and textbooks laid out page by page may be rejected, or arrive with pages split, shrunk or out of order. Publisher fonts are a gamble: sometimes they survive as a Publisher Font option, sometimes the book falls back to Bookerly. Complex tables, SVG drawings, embedded audio and video, and anything scripted are simplified or dropped. A book with no proper navigation file can arrive without a working table of contents even though the chapters are all there.

DRM is a hard stop. EPUBs bought from Kobo, Google Play Books, Apple Books or most library lending services carry Adobe or store-specific copy protection, and Send to Kindle rejects them. No converter can legitimately help, including the one on this site, so those books stay in the store's own app.

The Kindle library does not read the file name the way a computer does. It takes the title and author from the metadata inside the EPUB, a small OPF file in the package. If those fields are empty or wrong, which is common with books exported from word processors or assembled by hand, the Kindle falls back to whatever it can find: the file name, an internal identifier, or Unknown as the author. A file called book_final_v3.epub with no metadata will be listed exactly like that.

The cover works the same way. The EPUB has to declare one of its images as the cover in the manifest; an image that merely happens to be first in the book is not enough on every device. Sent books also sit in the Docs collection, not with store purchases, so if one seems to be missing, look under the documents filter in the library before re-sending it.

The fix is to correct the metadata before you send, not after. Calibre's Edit metadata dialog does it on a computer, and the e-book converter can write Title and Author under Advanced settings while keeping the format as EPUB, with Cover set to Keep cover so the cover image is declared properly.

Send to Kindle is the right default for most books, but there are good reasons to skip it. You may not want an Amazon account involved at all, or you read on a Kindle that never connects to Wi-Fi. A book with carefully designed typography may come back flattened by Amazon's conversion, while your own AZW3 keeps embedded fonts and most of the CSS. Large comics and illustrated books can exceed the email limit or arrive badly paginated. And if you manage a library in Calibre, sideloading over USB keeps that library the single source of truth.

In each of those cases, convert the DRM-free EPUB to AZW3 and copy it into the documents folder on the Kindle by cable. You can do that in Calibre, or with EPUB to AZW3 in the browser, where Reading device sets image sizes for a basic Kindle, a Paperwhite or Oasis, or a Scribe. The trade-off is sync: a sideloaded file lives on one device, so reading position, highlights and notes do not follow you to your phone.

MOBI is only worth making for the first three Kindles, the original, the Kindle 2 and the Kindle DX, which never received KF8 support. For those, use EPUB to MOBI and accept plainer formatting.

Send to Kindle also accepts PDF, but a PDF behaves very differently once it arrives. EPUB is reflowable: the text rewraps to the 6 or 7 inch screen, you choose the font size, and margins adjust. A PDF is a set of fixed pages, usually designed for A4 or US Letter paper, so on a Paperwhite each page is shrunk to fit and the text ends up tiny. You can zoom and pan, but reading a whole book that way is tiring. Only a large-screen Kindle Scribe makes ordinary PDFs comfortable.

If you have both versions of a book, send the EPUB. If you only have a PDF of a text-heavy document, typing convert as the email subject asks Amazon to turn it into a reflowable Kindle document, which works for simple layouts and mangles columns, tables and footnotes. The same problem shows up with any PDF conversion, as our guide on converting PDF to Word explains: fixed pages carry position, not structure, so the result depends on how clean the source is.

Most failures leave a trace. When Amazon cannot deliver a document sent by email, it usually replies to the sender with a short explanation, so check that inbox, including spam, before you change anything. Silence after an email almost always means the sending address is not on the approved list. Web and app uploads report errors on screen. Work through the causes below in order; the first two cover most problems.