Free Text Compare (Diff Checker)
Paste two versions of a text and see every change highlighted word by word, with a similarity score. Free, instant, and fully private.
A text compare tool — also called a diff checker — highlights exactly what changed between two versions of a text: every added and removed word, plus a similarity score. Humanit’s free tool compares line by line, refines word by word, and runs entirely in your browser, so neither version is uploaded.
How it works
- 1Paste the original. Drop the first version of your text into the “Original” box.
- 2Paste the revised version. Drop the second version into “Revised” — the comparison runs automatically.
- 3Read the highlights. Removed words appear struck through in red, added words in green, with a similarity score and change counts on top.
How the comparison works
The tool first lines up the two versions paragraph by paragraph, then compares each changed passage word by word — the same longest-common-subsequence approach code-review tools use, applied to prose. Unchanged text stays plain, removed words are struck through in red, and added words are marked in green, so a glance shows what your edit (or your editor) actually did. Two texts that differ only in spacing or blank lines are reported as identical.
What the similarity score means
The score is the share of words the two versions have in common, in order — 100% means word-for-word identical, and around 50% means half the wording changed. It measures wording, not meaning: a paraphrase that rewrites every sentence scores low even when the meaning is untouched. That makes it useful for judging how heavy an edit was, and useless for judging whether the edit was faithful — read the highlights for that.
Review AI edits before you accept them
The most useful habit this tool enables: whenever an AI rewrites something for you — a humanized paragraph, a paraphrase, a grammar fix — paste the before and after here and read exactly what changed. It takes thirty seconds, catches the places where a rewrite drifted from what you meant, and keeps you the author of the final text rather than a spectator to it. It works just as well for reviewing a human editor’s changes or comparing two saved drafts.
Free, unlimited, and private
The text compare is free with no sign-up and no limit on how much text you process. Because it runs entirely in your browser, your text is never sent to a server, stored, or used to train any AI — it never leaves your device. When you’re ready to do more with your writing, Humanit’s AI humanizer and AI detector are one click away.
| You see | It means |
|---|---|
| Struck-through red text | Removed from the original |
| Green text | Added in the revised version |
| Plain text | Unchanged in both versions |
| Similarity % | Share of words the two versions have in common |
Frequently asked questions
Can I compare two documents with it?
Yes — open both documents and paste their text into the two boxes. There is deliberately no file upload: the comparison runs in your browser, and your documents never leave your device.
Is the comparison case-sensitive?
Yes. “The” and “the” count as a change, so capitalization edits stay visible instead of being silently ignored.
Is there a limit on text size?
No hard limit. Extremely large pastes fall back from word-level to line-level comparison so your browser stays responsive — the tool tells you when that happens.
Why does a paraphrase score so low on similarity?
The score measures shared wording, and a paraphrase changes wording by design. A low score with meaning intact just means the rewrite was thorough — read the highlights to confirm nothing important drifted.
Do I need an account?
No. There’s no sign-up and no install — open the page and start typing.
Does it work on mobile?
Yes — it works in any modern browser on phone, tablet, or desktop.
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Open the AI HumanizerLast updated: August 2026