difft

syntax-aware structural diff tool

TLDR

Compare two files with structural diffing

$ difft [old_file] [new_file]

Compare files with side-by-side output

$ difft --display side-by-side [old_file] [new_file]

Show only changed lines (inline display)

$ difft --display inline [old_file] [new_file]

Compare with specific language parsing

$ difft --language [rust] [old.rs] [new.rs]

Compare directories

$ difft [old_directory] [new_directory]

Use with git diff

$ git diff --external-diff difft

Set as default git diff tool

$ git config --global diff.external difft

Compare and skip unchanged sections

$ difft --skip-unchanged [old_file] [new_file]

difft (Difftastic) is a structural diff tool that understands programming language syntax. Unlike line-based diff tools, it parses source code and compares the actual structure, showing meaningful changes while ignoring formatting differences.The tool builds abstract syntax trees (ASTs) for both versions of a file, then computes the minimal structural difference. This means it can recognize when code is moved or refactored without treating it as completely different, and it won't flag changes that are purely whitespace or formatting.Difftastic supports over 50 programming languages with dedicated parsers built using tree-sitter. For unsupported files, it falls back to a text-based diff. Language detection is automatic based on file extension, but can be overridden.The side-by-side display shows old and new versions in parallel columns with colors indicating additions (green), deletions (red), and modifications. The inline display shows changes in a more compact format. Git integration allows using difft as the external diff tool.

PARAMETERS

--display mode

Output format: side-by-side, side-by-side-show-both, inline (default).

--language lang

Force a specific language parser (auto-detected by default).

--list-languages

Show all supported languages.

--skip-unchanged

Don't show unchanged parts of the file.

--context n

Number of context lines (default: 3).

--width n

Maximum display width (default: terminal width).

--color when

Color output: always, never, auto.

--background type

Background color: light, dark (default: dark).

--syntax-highlight on|off

Enable or disable syntax highlighting.

--tab-width n

Tab display width (default: 4).

--parse-error-limit n

Maximum number of parse errors before falling back to text diff.

--byte-limit n

Skip files larger than this size.

--graph-limit n

Maximum graph size for structural diff algorithm.

--exit-code

Set exit code to 1 if there are syntactic changes (useful in scripts).

INSTALL

sudo dnf install difftastic

sudo pacman -S difftastic

sudo apk add difftastic

sudo zypper install difftastic

brew install difftastic

nix profile install nixpkgs#difftastic

CAVEATS

Large files or very different structures may hit performance limits. Parse errors cause fallback to text diff. Some language features may not be perfectly parsed. Extremely complex structural changes may produce hard-to-follow output.

HISTORY

Difftastic was created by Wilfred Hughes starting in 2020. It was developed to address the limitations of line-based diffs, which often produce noisy output for refactoring or reformatting changes. The tool uses tree-sitter parsers for language-aware structural comparison and has gained popularity as a git diff replacement.