Fix ePub

This is a simple tool written in Rust to correct ePub file problems for use with Amazon Kindle devices. This was inspired heavily by https://kindle-epub-fix.netlify.app/ whose JS source is available: https://github.com/innocenat/kindle-epub-fix

Usage

cargo build --release
./target/release/fixepub book.epub another-book.epub
./target/release/fixepub --language fr-CA book.epub
./target/release/fixepub --force book.epub

Each input produces a -fixed file alongside the original. Existing output files are protected unless --force is supplied. Output is committed only after the whole repair succeeds; failed repairs leave existing files intact.

The tool removes images without a nonempty src, removes link fragments that point to a chapter's body ID, ensures XHTML has an XML declaration, and repairs missing or invalid package language metadata. The fallback language defaults to en; use --language to choose another valid BCP 47 tag. Valid language metadata is preserved.

Documents are parsed as XML, preserving namespaces, comments, and CDATA. Supported input encodings are decoded without character replacement and modified documents are emitted as UTF-8. Malformed XML and unsupported encodings cause an error that identifies the document, instead of producing potentially damaged output.

Unchanged entries are copied in their compressed form. Binary assets are never loaded into memory, and document processing holds only one document at a time. The mimetype entry is written first and uncompressed.

Development

Linux releases are static musl binaries for x86-64, built with Nix. They do not require Nix or distribution-specific shared libraries. Build one on Linux with nix build .#static; the binary is at result/bin/fixepub. CI runs its tests and checks that it starts in Alpine and Debian containers without Nix installed.

cargo test --locked
cargo clippy --locked --all-targets -- -D warnings
cargo fmt --check

nix flake check also runs the test suite through nextest.