Difftastic is an experimental structured diff tool that compares files based on their syntax.

See the manual to get started.

Difftastic supports the following languages:

• C
• C++
• C#
• Clojure
• CSS
• Elixir
• Emacs Lisp
• Go
• Haskell
• Java
• JavaScript (and JSX)
• JSON
• OCaml
• Python
• Rust
• TypeScript (and TSX)

If a file has an unrecognised extension, difftastic uses a line-oriented diff.

Known Issues

Robustness. Difftastic is young and each release has fixed several crashes.

Comprehensible display. Minimal diffs can be confusing: replacing one function with another may have a small amount of common punctuation even though they're completely unrelated. Alignment of slightly modified lines is a major challenge too.

Changes to long lines. Difftastic uses a side-by-side display by default, which is unhelpful if the only changes are near the end of a line.

Performance. Difftastic scales relatively poorly on files with a large number of changes, and can use a lot of memory. This might be solved by A* search.

Non-goals

Patch files. If you want to create a patch that you can later apply, use diff. Difftastic ignores whitespace, so its output is lossy. (AST patching is also a hard problem.)

License

Difftastic is open source under the MIT license, see LICENSE for more details.

Files in sample_files/ are also under the MIT license unless stated otherwise in their header.

Further Reading

The wiki includes a thorough overview of alternative diffing techniques and tools.