Editing and proofreading
Compare a rough draft with the polished version. Every word, sentence, and paragraph that changed is right there, no hunting.
Input
Output
What is Compare Text?
Compare Text is an online tool that takes two pieces of text and shows you exactly what changed between them. Paste an old version on one side and the new version on the other; differences light up in colour. Green means added, red means removed.
It works for anything plain text — paragraphs of writing, code snippets, configuration files, contract clauses, translations. Lines that match stay neutral, so your eye goes straight to what's different.
Use it when you don't want to open a heavy desktop tool but you do want accurate results in one click. No signup, no upload, and no record of what you compared.
What it does
Compare Text takes two pieces of text and highlights what was added in green and what was removed in red. It does the work character-by-character, so a single missing comma or a renamed variable shows up clearly. The general technique is called a diff.
The algorithm is Google's diff-match-patch, the same engine behind Google Docs revision history. We picked it because it handles natural language and code equally well, and the Apache 2.0 licence means we can ship it without restrictions.
There's no server. Your text is read by JavaScript using the FileReader API, compared in memory, and the result is drawn back into the page. Close the tab and it's gone.
How to compare two texts
Three steps. The diff updates as you type, so there's no compare button to press.
- 1
Add the original
Paste it into the left panel, or click Upload to load a .txt or .md file. Sample drops in a short example if you just want to see the tool in action.
- 2
Add the updated version
Paste or upload it on the right. As soon as both panels have content, deletions show up in red on the left and additions in green on the right.
- 3
Review the changes
Scroll either side, both panels stay in sync. The header tells you how many changes were detected. Copy or Download either text once you're happy with the result.
When this is useful
Quick code diffs
Two versions of a function or a config snippet. Faster than opening a git client when you only need to eyeball a few lines.
Document revisions
Track what changed between V1 and V2 of a policy, contract, or readme without rereading the whole thing.
Translation review
Original on one side, the editor's corrections on the other. Useful for spotting patterns and improving the next round.
Frequently asked questions
Does this save my text?
No. The whole comparison runs in your browser. Nothing is sent to a server, logged, or stored.
Is there a size limit?
Practical limit is your device's memory. Small and medium texts diff instantly. A few hundred KB still works but takes a second or two.
What kind of differences are detected?
Character-level changes, then grouped at word boundaries when possible (semantic cleanup). Insertions are green, deletions red.
Can I upload a file?
Yes. Click Upload on either panel for plain-text files (.txt, .md, .csv, etc.). The file replaces whatever's in that panel.
Does it work offline?
Once the page is loaded, yes. The diff runs locally, so a flaky connection doesn't affect it.
Why are short common words sometimes matched between unrelated text?
Character-level diff aligns short common substrings (the, a, punctuation) wherever it can. The semantic cleanup pass reduces this, but two completely unrelated texts will still produce a fragmented-looking result. That's expected.