Compare code by syntax tokens or exact lines

Capability overview

How can I use language-aware code comparison in Diff Anything?

Switch between Smart Diff and the conventional Line Diff while keeping normal syntax highlighting, exact source text, editing, moved blocks, wrapping, and compact context visible. Detection uses filenames, extensions, shebangs, and pasted content.

Smart Diff uses language-family-aware token alignment across all 117 non-plain-text editor languages. It ignores safe layout-only edits in brace and expression languages, preserves significant indentation and statement newlines, and treats strings and comments according to the selected language. It is not an AST comparison and does not claim compiler-level semantic equivalence.

Code is detected from filenames, extensions, shebangs, and pasted content. Shared extensions are disambiguated from content, and framework files can highlight embedded implementation languages instead of falling back to plain text.

The maintained editor catalog includes 18 additional languages in 1.5: Ada, Assembly, COBOL, Crystal, CUDA, D, Elm, Erlang, Fortran, GLSL, Haskell, Haxe, HLSL, LaTeX, LLVM IR, OCaml, Raku, and WebAssembly text.

The CLI provides a Unicode-safe highlighted terminal view with automatic or forced colour, an explicit language override, and configurable context around each hunk.

Smart or Line

When to read a change in Smart and when to read it in Line

Code review gets hard when a formatter touches a file. A wrapped function call, a re-indented block, or a brace moved to its own line can turn a one-word fix into forty changed lines. The Smart view drops those layout-only edits and highlights the tokens that actually changed, so the fix is easy to find again.

The Line view shows each line exactly as it is stored. Use it when whitespace is the change you care about, when you want to confirm a hunk before copying it across, or when you need to match line numbers with a code review tool. Both buttons sit next to each other in the text toolbar, and switching between them keeps both files and any edits you have made.

Hover over Smart to see a short summary, either the number of changed tokens or a note that the change is formatting only. Smart needs both sides in the same language. When the two files are detected as different languages, or as plain text, the Smart button is unavailable and the Line view is used.

Language detection

How the language is chosen, and how to change it

The Code language menu shows what was detected, for example Auto · TypeScript. A language you pick there wins over everything else and applies to both sides at once, which changes the highlighting and the rules Smart uses for strings, comments, and whitespace.

Without a manual choice, Diff Anything checks known filenames such as Dockerfile or Cargo.toml, then the extension, then the content when an extension is shared by several languages. That is how a .m file is told apart as MATLAB or Objective-C and a .h header as C or C++. Extensionless scripts are recognised from their shebang line, and pasted snippets from typical language markers.

Vue, Svelte, Astro, and Blade templates keep highlighting for the script and style sections inside them, instead of showing the whole file as plain markup.

Review controls

Toolbar controls for long or restructured files

Each control is a toggle in the text toolbar and can be combined with either view:

• Moves connects a block of code that was moved to a new place instead of showing it as a deletion and an addition.
• Compact collapses long unchanged stretches so the changed hunks sit closer together.
• Wrap breaks long lines, which helps with minified or generated code.
• Whitespace makes spaces and tabs visible when indentation is the question.
• Side by side and Inline switch between two columns and a single merged column.
• The Ignore menu adds Ignore whitespace, Ignore blank lines, Ignore case, and line-ending normalization for the line comparison.

Scope and plans

What Smart compares, and what the free plan includes

Smart works on tokens with rules for each language family. It keeps indentation in Python-like languages and statement line breaks in shell scripts, but it does not build a syntax tree, so it cannot tell you that two different implementations behave the same way.

Code comparison, both views, editing, and saving are part of the free plan for files up to 5 MB per side and 10 new comparison sessions per day. Pro removes those limits. The command line can print the same highlighted comparison in a terminal, with --language to force a language and --context to set how many unchanged lines surround each hunk.

In the workflow

How to use it

1. Open both versions

   Open Left and Open Right, drop two files on the window, or paste a snippet into each side.

2. Check the language

   Look at the Code language menu and pick a language if the file is unusual or pasted without a name.

3. Read it in Smart

   Use Smart to find the real edits in a reformatted file, and turn on Moves if code was reorganised.

4. Confirm in Line

   Switch to Line before copying a hunk across, then save the modified file.

Useful in practice

When to use it

Related manual

Choose the right comparison mode

Choose sources, understand automatic detection, and select the engine that answers the question you are actually asking.

Direct answers

Questions about language-aware code comparison.