DRM, Format Conversion & Calibre
Calibre, Sigil, epubcheck, DeDRM tools — convert, edit, and own your books.
Calibre is the swiss-army knife: format converter, library manager, metadata editor, server, news downloader, and more. It's free, OSS, and the single most important reading tool not on a device. This page also covers DRM honestly — Calibre + the DeDRM toolkit can format-shift books you own; the legality varies by jurisdiction. We don't recommend piracy. Pair with Self-Host Libraries, KOReader, and Public-domain sources.
Calibre
- ★ ★ Calibre — free OSS (GPLv3); Win / Mac / Linux desktop; library manager + format converter (EPUB / MOBI / AZW3 / PDF / CBZ / DOCX / HTML / RTF / TXT / DJVU); metadata fetcher; news downloader (turns RSS / web sites into EPUB); built-in viewer; built-in Content Server with OPDS + web reader; Send-to-device. The most-installed reading app of all time outside the big-store readers.
- ★ Calibre-Web — see Self-Host Libraries.
Format / metadata tools
- ★ Sigil — free OSS; EPUB editor; desktop; the WYSIWYG / code-view EPUB authoring tool.
- PageEdit — companion WYSIWYG for Sigil.
- epubcheck — free OSS; W3C-blessed validator; flags malformed EPUBs.
- kepubify — free OSS; convert EPUB → KEPUB (Kobo's flavour) for better Kobo behaviour.
- ebook-convert (Calibre CLI) —
ebook-convert in.pdf out.epubdoes most of what people install GUI converters for. - mutool / mupdf — free OSS; PDF → text / EPUB / images.
- Pandoc — free OSS; the swiss-army doc converter; Markdown ↔ EPUB ↔ HTML ↔ PDF.
Online converters (paid + free, easier for one-offs)
- Online-Convert — paid + free tier; many formats.
- Zamzar — paid + free; same.
- CloudConvert — paid + free; cleaner UI.
- All of the above re-upload Calibre under the hood for many formats; just install Calibre.
DRM realities (honest)
- Kindle DRM (AZW3 / KFX / topaz) — Amazon's; tied to your account.
- Adobe DEDRM (EPUB / PDF) — used by Kobo, Google Play, public-library EPUBs, B&N Nook.
- Apple FairPlay — Apple Books DRM.
- Audible AAX / AAXC — see Audiobooks.
DeDRM tools (legal grey)
- ★ DeDRM_tools — free OSS; Calibre plugin; strips DRM from books you own for format-shifting / backup. Legal in some jurisdictions for personal use, illegal in others (notably the US under DMCA §1201, with a triennial Library of Congress exemption that's been partially granted for accessibility / format-shifting in some recent rulings — but the field is unsettled). Don't redistribute. Don't use for piracy.
- We won't tell you what to do with your own books; we will tell you to read your local law.
Send-to-device + cloud
- Send to Kindle (Amazon) — free; accepts EPUB since late 2022.
- Send to Kobo via Pocket — built-in.
- Calibre wireless device API — talks to KOReader / Calibre Companion.
- Syncthing / Resilio — sync
~/Booksbetween desktop and Boox / rooted Kindle / Linux.
Patterns
- ★ One Calibre library = source of truth. Devices are caches; Calibre is the master.
- Convert once, sideload many — keep EPUB masters; convert to AZW3 / KEPUB on send.
- Backup the Calibre folder —
~/Calibre Library(or wherever); it's all flat files + one SQLite DB. - Validate EPUBs with epubcheck before publishing; bad EPUBs render badly on e-ink.
- News-as-EPUB: Calibre's news downloader is criminally underused — get the daily NYT delivered to your Kindle for free.
Anna's Archive / shadow libraries (we don't recommend)
- Anna's Archive, Library Genesis (LibGen), Sci-Hub, Z-Library — pirate shadow libraries; widely used; legally infringing in essentially every jurisdiction; we don't link or recommend. Mentioned because pretending they don't exist is dishonest. Use Project Gutenberg / Standard Ebooks / Internet Archive instead — see Public Domain.
Pick this if…
- Default FOSS library + converter: Calibre.
- EPUB editor: Sigil.
- Kobo-flavoured EPUB: kepubify.
- Universal doc conversion: Pandoc.
- Validate EPUB: epubcheck.
- Format-shift books you own: DeDRM_tools (jurisdiction permitting).