Online Tool Store
Semantic Diff for Code
Compare two code snippets after stripping comments and normalizing whitespace, so only real logic changes are highlighted in a token-level diff.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
How the Semantic Diff for Code works
- Paste two versions of a code snippet into the two panels.
- Both are stripped of comments and re-tokenized so formatting differences (indentation, line breaks, spacing) don't count.
- The remaining token streams are compared with a longest-common-subsequence diff, highlighting only additions and removals that represent real code changes.
Why token-level, not line-level
A traditional line diff flags a reformatted line as fully changed even if only one character moved. Comparing at the token level after stripping comments surfaces the actual logic change and skips pure formatting noise — closer to what a code reviewer actually cares about.
FAQ
How does it "ignore" whitespace and comments?
Before comparing, both snippets are stripped of // and /* */ style comments and re-tokenized, collapsing runs of whitespace and reformatting into a normalized token stream. If the token streams match exactly, the tool reports the snippets as semantically identical even though the raw text differs.
Does it understand code structure like a real AST diff?
No. This is a token-level comparison, not a language-aware parser — it works reasonably well across many C-like languages (JS, Rust, Java, Go, etc.) but won't catch semantic equivalences like reordered independent statements or renamed variables.
Is my code sent anywhere?
No. Both snippets are tokenized and diffed entirely in your browser with a longest-common-subsequence algorithm — nothing is uploaded.
How we compare
| Feature | Online Tool Store | git diff -w | Full AST diff tool |
|---|---|---|---|
| Ignores comment-only changes | ✓ | ✗ | ✓ |
| No install required | ✓ | ✗ | ✗ |
Use this for a quick "did anything actually change" check before a code review; use a language-specific AST diff tool when you need guarantees about structural equivalence.