Kindle DRM Checker
AZW · AZW3 · MOBI · Client-side
A Kindle file either has Amazon's DRM or it doesn't, and the answer sits in two bytes of the header. Drop the file in to read them. If it is unencrypted, it opens in GemReader and every other reader; if not, only the Kindle app on the buying account can open it.
Drop an AZW, AZW3 or MOBI file here
The file is read in your browser and never leaves your device — no upload, no server, nothing stored.
Which Kindle files are DRM-free
Bought from Amazon:almost always locked, whichever extension it has. A few publishers opt out of DRM on Amazon, but the file still arrives as KFX, which only Amazon's apps read.
Converted with Calibre, downloaded from Project Gutenberg, Standard Ebooks or a DRM-free store, or sent to you as a .mobi:unencrypted. These are the files that show “No DRM” and import straight into GemReader's library.
If it is locked, the honest options are the Kindle app or a DRM-free copy from another store. Stripping the DRM is a legal grey area in most countries and not something this site helps with. For EPUBs, the same question is covered in how to check if an EPUB has DRM.
Questions
How does it know whether the file has DRM?
Every MOBI-family file carries a PalmDOC header in its first record, and two bytes at offset 12 of that header record the encryption type: 0 is unencrypted, 1 is the old Mobipocket scheme and 2 is Amazon's. The checker reads those two bytes and nothing else about the book.
What about .kfx files?
KFX is Amazon's newer container and does not use the PalmDOC header. Every KFX delivered by Amazon is DRM-protected, so if the file came from the Kindle app or a Send-to-Kindle download, assume it is locked. The checker reports it as an unrecognised format rather than guessing.
I bought the book. Why can't I open it elsewhere?
Because Amazon DRM ties the file to the Kindle app and the account that bought it — that is what it is for. No third-party reader on any platform can decrypt it. Some publishers sell the same title DRM-free elsewhere; that is the copy to look for.
The result says the DRM status is unreadable.
The header did not parse, which nearly always means a truncated or partially downloaded file rather than DRM. Re-download it. If Calibre opens it, it is fine.
Is the file uploaded to check it?
No. It is read with JavaScript in your browser tab. Only the first few hundred bytes are even looked at, and nothing leaves your device.