Is MOBI still supported in 2026?

No. Amazon officially deprecated MOBI in 2023. KDP no longer accepts MOBI uploads, and newer Kindle firmware no longer renders MOBI files. If you have old .mobi files, convert them to EPUB.

What replaced MOBI on Kindle?

Amazon uses AZW3 (KF8) internally for Kindle books, and accepts EPUB via Send to Kindle. For self-publishers, submit EPUB to KDP — Amazon handles the conversion.

Can I still open a .mobi file I have on my old Kindle?

Older Kindle firmware (pre-2023) can still read MOBI files stored locally. Newer devices may not render them correctly. Convert the MOBI to EPUB using Calibre to ensure long-term compatibility across all readers.

Why did EPUB win over MOBI?

EPUB is an open standard, platform-neutral, and actively maintained by the W3C. MOBI was a proprietary format Amazon acquired from Mobipocket in 2005 — maintaining a proprietary format while the ecosystem shifted to open standards wasn't sustainable.

EPUB vs MOBI: Complete Comparison

Convert EPUB to PDF →

MOBI is dead. Amazon deprecated it in 2023 — no new uploads to KDP, no reason to create new files. If you came here wondering whether MOBI is relevant to something you're doing today, the answer is almost certainly no. Use EPUB.

What MOBI Was

MOBI was a proprietary ebook format Amazon licensed from Mobipocket in 2005 to power early Kindles. It was always Kindle-only, technically limited (650KB file size cap on older devices, no audio/video, no EPUB 3 features), and entirely controlled by Amazon. It served its purpose for 15+ years, then Amazon replaced it internally with AZW3 and then KFX.

In 2022 Amazon started accepting EPUB directly via Send to Kindle. In 2023 they closed MOBI submissions to KDP. That's the end of the format's relevance.

Format Status Today

Format	Status	Use it if…
EPUB	Active W3C standard	Distributing or reading ebooks on any platform
MOBI	Deprecated 2023	You have old files and need to read them (convert to EPUB)
AZW3	Legacy Kindle format	USB transfer to Kindle devices made before ~2018
KFX	Current Kindle internal format	You don't — Amazon creates this from your EPUB automatically

Should You Still Use MOBI in 2026?

No. MOBI is deprecated. Amazon stopped accepting MOBI uploads to KDP in 2023. Every platform that required it has moved on:

Kindle devices and apps: Accept EPUB via Send to Kindle — Amazon converts to KFX automatically
KDP: EPUB only — MOBI is rejected at upload
Everything else: Apple Books, Kobo, Play Books — never supported MOBI

If you have existing MOBI files, convert them to EPUB in Calibre: import, Convert Books, output format EPUB. Run the result through the validator and clean up metadata with the metadata editor if needed.

AZW3 and KFX

Amazon's current internal format is KFX. When you send EPUB to Kindle, Amazon converts it to KFX server-side. You never touch KFX. AZW3 is a legacy intermediate format — you might see it in old Kindle libraries but there's no reason to create new AZW3 files unless you're doing USB transfers to very old devices (pre-2018), where it's slightly better supported than MOBI anyway.

The Kindle format timeline, for context: MOBI (2000) → AZW (2007, DRM-wrapped MOBI) → AZW3/KF8 (2011) → KFX (2015) → EPUB accepted as input (2022). The internal format doesn't matter to you as a publisher or reader.

Sending EPUBs to Kindle

Email your EPUB to your Kindle address — Amazon converts it and delivers it over Wi-Fi. Full process: EPUB to Kindle guide. Validate your EPUB first and check metadata so the title and author appear correctly in your library.

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