Text Diff

Why a text diff matters

A diff tool shows you exactly what changed between two versions of a piece of text: lines added, lines removed, lines that stayed the same. It's the most honest way to compare two documents — not "they look similar" but "here are the seventeen differences, character by character." Every code review, every git pull, every config rollback is built on top of a diff somewhere.

This tool runs entirely in your browser. Paste two versions, see the changes highlighted in green and red, with running counts of additions and deletions.

When you reach for it

• Comparing two API responses. Hit a staging endpoint and a production endpoint with the same request, paste both responses, see what's different.
• Catching a typo in a paragraph. Two versions of a sentence look identical to your eye but the diff reveals an extra space, a swapped word, a different smart-quote.
• Finding the change someone made. A teammate forwards you "the latest version" of a doc, you have last week's copy, you want to see what they edited.
• Debugging config drift. The dev environment works, prod doesn't — paste both .env files (with secrets stripped) and the missing variable jumps out.
• Verifying a paste. You copied a long string from one place to another and want to confirm nothing got truncated.

How to read the output

Standard diff convention applies. Lines added in the second version are highlighted in green and prefixed with +. Lines removed (present in the first, absent in the second) are red, prefixed with -. Unchanged lines are shown with no marker, providing context around the changes.

If a line was modified rather than added or removed, most diff algorithms will represent that as one deletion and one addition — not as a partial change. This is correct but can be surprising on long lines where only one word differs.

Limitations of line-based diffing

A line-based diff treats each line as an atomic unit. That works beautifully for code (where lines are the natural unit) but less well for prose, where a single sentence might wrap across multiple lines after editing. For prose, sometimes joining everything to one line per paragraph before pasting gives a more useful comparison.

For very-fine-grained comparison — word by word or character by character — you'd want a different tool. This one is line-oriented because that's what's useful 95% of the time.

Privacy

The diffing happens locally in your browser. Nothing you paste is sent anywhere or stored. This matters for the cases where you'd otherwise hesitate — comparing two versions of a contract, two API responses with PII, two snippets of proprietary code — using an online diff tool that doesn't tell you where your data goes.