What diff algorithm is used?

A longest-common-subsequence based line diff, well suited to small and medium snippets.

Can I diff whole files?

Yes, paste any text — very large inputs may be slower since the algorithm is O(n·m).

Does it show character-level changes?

No, this tool compares whole lines rather than individual characters.

Is my data uploaded to a server?

No. This tool runs entirely in your browser using standard web APIs, so your input never leaves your device and nothing is logged or stored on our servers.

Does it work offline and on mobile?

Yes. Once the page has loaded it keeps working without a network connection, and the layout is responsive so it stays usable on phones and tablets.

Code Diff Merger

Side-by-side line diff of two code snippets with stats.

Support

Works Offline

Privacy First

No Login

No API

Original

Modified

Diff

Side-by-side line diff

Added

Removed

-1

Unchanged

function greet(name) {

console.log('Hello ' + name);

}

function greet(name) {

console.log(`Hello, ${name}!`);

return true;

}

About the Code Diff Merger

Compare two blocks of code or text line by line with a side-by-side highlighted diff, and see counts of added, removed, and unchanged lines.

Examples

Compare functions

old code

Output

highlighted diff with +/- stats

Keyboard shortcuts

Copy the main outputCtrl / ⌘ + Shift + C
Download the resultCtrl / ⌘ + S
Share this toolCtrl / ⌘ + Shift + S
Reset the inputsAlt + R
Open the tool search paletteCtrl / ⌘ + K

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Frequently asked questions

Version 1.0.0 · Updated 2026-08-06 · Runs entirely in your browser