Quick Answer
A code diff checker compares two versions of a file and shows exactly which lines were added, removed, or left unchanged. Paste both versions, read the colored diff, and see a similarity score at a glance.
What This Tool Does
The tool runs a longest-common-subsequence diff over the two texts and renders each line with a marker: + green for added, − red for removed, plain for unchanged. Stats show how many lines fall in each bucket plus an overall similarity percentage.
Key Features
- Line-level diff — added, removed and unchanged lines are color-coded.
- Similarity score — a percentage that summarizes how close the versions are.
- Swap button — flip A and B to review from the other side.
- Fast — the diff runs locally, even on long files.
How to Use the Code Diff Checker
- Paste the original code in Version A.
- Paste the changed code in Version B.
- Read the diff below — added lines are green, removed lines are red.
- Click Swap A & B to view the diff from the other direction.
Use Cases
- Reviewing what changed between two configs or two versions of a script.
- Checking that only the intended edits landed in a copied file.
- Quick before/after comparison without opening a Git client.
Tips
- Whitespace differences count as changes — normalize indentation first if you only care about logic.
- The similarity score is a rough guide, not a legal definition of "same file".
- For real projects, Git diff is still the authority; this tool is for quick pasted comparisons.
Privacy
The diff runs locally — your code never leaves the browser.
Conclusion
See what changed in seconds: paste, compare, read the colors. Free and private.