rars

A Rust implementation of RAR.

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rars is free software for compression, decompression and recovery of RAR archives. It supports all the archive types I could find - from the early RE~^ ones from the DOS days all the way through to RAR 7. It comes with a Rust library, a CLI, Python and TypeScript bindings.

It started as an agentic development experiment, and has since matured as it gained some users. It's still a bit slower than WinRAR, uses more memory and has slightly worse compression. It could use more testing at volume, too. Other than that it's in pretty good shape.

Usage

The API is in the rars crate, which is used by the Python and TypeScript bindings. For the CLI, run:

cargo install rars-cli.

To inspect, test, and extract archives:

rars info archive.rar
rars test archive.rar
rars x archive.rar out/

These commands accept parsing and decoding limits; see CLI reader controls.

To create archives with a specific RAR generation:

rars a --format rar29 archive.rar files...
rars a --format rar29 --solid --auto-filter archive.rar files...
rars a --format rar70 --store --volume-size 10m archive.part1.rar files...

The writer supports stored and compressed members, split volumes, passwords, comments, RARVM filters, RAR5 quick-open records, recovery records and header encryption. There are a lot of things I won't list here, so run rars --help for more details.

On Unix, native filenames and legacy archive names can contain non-UTF-8 bytes. The CLI, Python extraction and Rust path adapters preserve those bytes. RAR5/7 filesystem inputs use the format's reversible Unix byte mapping; member metadata and lookup keys retain the encoded archive identity. Use byte names (or Python RarInfo objects) for exact lookup, rather than lossy display names.

Legacy code pages are not guessed. Windows supports Unicode names; extracting non-Unicode legacy byte names there still requires caller-selected decoding. Use --legacy-name-encoding cp850 or the corresponding binding option; see legacy filename decoding for supported encodings and preservation semantics.

Library features

All features are enabled by default. For a sequential reader without encoders, recovery algorithms, cryptographic dependencies or Rayon:

[dependencies]
rars = { version = "0.10", default-features = false }

Enable encrypted reading independently when needed:

rars = { version = "0.10", default-features = false, features = ["encryption"] }

Every combination is supported. Writing encrypted archives requires write and encryption; writing recovery records requires write and recovery. Recovery repair works without write. Without parallel, buffered extraction APIs use sequential execution; bare WebAssembly also runs sequentially. Writing and recovery enable entropy support, including encrypted header reconstruction during repair; encrypted reading alone does not need entropy.

Without encryption, plaintext headers still expose encrypted member metadata. Opening encrypted headers or extracting encrypted payloads returns Error::FeatureDisabled { feature: "encryption" }, even if a password is supplied. Recovery operations similarly return a disabled-feature error without recovery. These errors have ErrorKind::UnsupportedFeature. Writer and encoder APIs are absent when write is disabled. RAR 1.3's fixed archive-comment transformation remains available to readers without encryption.

Cargo unifies features across consumers of the same crate. Another dependency that enables rars defaults can therefore restore the full build. Use cargo tree -e features to inspect the resolved configuration. The CLI, Python and npm bindings retain their full builds. See the independent consumer checks for reproduction commands that avoid workspace feature unification.

Reader resources

Reader workspace limits are available as Rust ArchiveReadOptions::with_max_reader_workspace_bytes, CLI --max-reader-workspace-bytes, Python ReadOptions(max_reader_workspace_bytes=...) and npm maxReaderWorkspaceBytes. They limit aggregate decoder workspace and queued parallel results across an extraction call or volume set. The default is unlimited. Logical output, parsed sources and caller output storage have separate costs; see the reader resource contract.

Writer execution

For writer execution modes, workspace estimates and retained storage, see WRITER_EXECUTION.md.

RAR5/7 writers accept an optional aggregate managed-memory ceiling: Rust WriterResources::with_max_memory_bytes, CLI rars a --max-memory 256m, Python RarBuilder(max_memory_bytes=256 << 20), and npm new RarWriter({ maxMemoryBytes: 256 * 1024 * 1024 }). The default is unlimited. This counts writer execution allocations and retained output, including binding copy peaks; caller inputs, sinks, runtime and allocator overhead are excluded. Legacy writers refuse the policy. Reader and rewrite staging limits are separate. See the resource contract for ownership boundaries and the separate estimated-workspace policy.

Bindings

Python bindings are published to pypi, so you can pip install rars. To build locally, it's just python.

RarBuilder.from_archive preserves supported RAR5/7 metadata and archive settings by default, plus a limited subset of ordinary RAR2.9–4.x archives. Unsupported preservation is rejected. Pass preserve=False explicitly to convert to unencrypted RAR5, including from older archives. This default change is intended for the next minor release; see the rewrite contract.

RarBuilder writes accept cancellation=rars.CancellationToken() for cooperative cancellation from another Python thread, with or without progress callbacks. Reader operations accept options=rars.ReadOptions(...) for cancellation, output ceilings and RAR5/7 decoder limits. See the reader controls and rewrite contract. Repair operations also accept cancellation=; see repair cancellation.

For JS it's built to WebAssembly and published to npm; npm install @bitplane/rars. It reads and writes in the browser and in Node, with no native module. To build locally, type just npm.

Licensed under the Apache License, Version 2.0.