Which Ebook Reader Books Formats Support Annotations?

I get a little giddy thinking about how flexible ebook formats can be, and the short version is: most modern formats support annotations, but how well they do it depends on the reader app/device and whether the file is DRM‑locked.

EPUB is the big generalist — it’s the standard on most non‑Amazon stores and readers. On apps like Apple Books, Google Play Books, Kobo, and many third‑party apps (Moon+ Reader, Librera, etc.), EPUB lets you highlight, add notes, and usually sync those annotations to your account. Kindle’s proprietary family (AZW, AZW3/KF8, and the newer Kindle formats) also fully support highlights and notes inside Amazon’s ecosystem — on Kindle devices and apps; those annotations are saved to the cloud and you can export or view them via 'My Clippings' or Amazon’s highlights page.

PDFs are tricky: they can absolutely be annotated, but it depends on whether the file is text‑searchable. Native PDFs (text layer present) let you highlight and comment in many readers; scanned images without OCR will block text selection and thus limit annotation. Lesser‑known formats like FB2, LRF, and plain TXT get basic annotation support in a lot of Android readers, though features vary. A big practical caveat: DRM will often tie annotations to an account or block export, and many readers store notes in their own databases rather than embedding them in the file. I usually keep a habit of exporting or backing up notes, especially for long reads I’ll revisit.