---
id: fastdiff
version: "0.3.0"
license: MIT license
license_treatment: permissive
maintenance: abandoned
---

# fastdiff — A fast native implementation of diff algorithm with a pure python fallback

License: permissive · Maintenance: abandoned · Downloads: 513.8K/mo

## What it is and what it does

Fastdiff is a diff algorithm library that uses WebAssembly compiled via Wasmer to accelerate text comparison operations. It wraps a native implementation and falls back to pure Python when WebAssembly is unavailable, aiming for cross-platform compatibility. The package depends on wasmer and wasmer-compiler-cranelift to provide the WebAssembly runtime.

The package is in pre-alpha status (Development Status :: 2) and has been abandoned since late 2022 with no maintenance activity for over three years. While it carries a permissive MIT license and installs with low friction, its lack of recent updates means it may not work reliably with current Python versions or modern wasmer releases.

Use it for:

- Comparing large text files or strings where performance is critical and you need faster-than-pure-Python diff operations
- Integrating diff functionality into applications where cross-platform WebAssembly acceleration is preferred over native C extensions
- Testing or prototyping WebAssembly-based algorithm implementations in Python environments

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Fastdiff provides a fast diff algorithm implementation using WebAssembly via Wasmer, with a pure Python fallback for compatibility.

No. The package is abandoned with no updates since 2022 and classifiers only claim support up to Python 3.7. While the MIT license is permissive and install friction is low, the lack of maintenance means compatibility with modern Python versions and wasmer releases is uncertain. Use an actively maintained diff library instead.

## Install

pip install fastdiff
uv add fastdiff
poetry add fastdiff

## Installing fastdiff

Before you install: Low install friction with a pure-Python wheel, but the package is abandoned as of 2022 with no updates in over three years. The last commit was 2022-12-26 and maintenance status is marked abandoned, so expect no bug fixes or compatibility updates for modern Python versions.

License in practice: MIT license is permissive and imposes no restrictions on use, modification, or distribution in your own projects.

Quickstart:

pip install fastdiff

import fastdiff
# Use fastdiff.diff() or comparable functions for text comparison

Requires wasmer and wasmer-compiler-cranelift as runtime dependencies; WebAssembly runtime must be available on your platform.

Verify before relying:

- Whether the package actually works with Python versions beyond 3.7 (classifiers list only up to 3.7; requires_python is unspecified)
- Current compatibility with modern wasmer versions and whether wasmer-compiler-cranelift is still maintained
- Whether the 75x speedup claim applies to typical use cases or only specific scenarios

## Package facts

- License: MIT license (permissive)
- Python support: unspecified
- Install friction: low
- Maintenance: abandoned
- Downloads: 513.8K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

diff algorithm implementation, fast text comparison, webassembly diff, sequence comparison, native diff performance, text diffing library, wasmer-based diff, webassembly, diff-algorithm, abandoned

[View on SkillFed](https://skillfed.io/packages/fastdiff) · [View on PyPI](https://pypi.org/project/fastdiff/)