To compare two texts, paste the original into one side and the changed version into the other, and a diff checker highlights every line and word that was added or removed. So you can see exactly what an editor changed without reading both versions line by line. The free text diff checker does it in your browser, side by side, with nothing uploaded.
Spotting the difference between two near-identical documents by eye is hard and unreliable. A single moved comma or a changed number hides easily in a wall of text. A diff does the comparison for you and points at the exact changes.
When you need a diff
The job comes up more than you would think:
- Document revisions. A colleague returns your draft with edits and no track-changes. A diff reveals what they touched.
- Contracts. Comparing two versions of an agreement to confirm only the agreed clauses changed, and nothing slipped in elsewhere.
- Code and config. Spotting the exact lines that differ between two snippets, two settings files, or two log outputs.
- Proofreading. Checking that an edit changed only what you intended and did not introduce a new typo.
In each, the point is certainty. You do not want to think two versions match; you want to see precisely where they do not.
How to compare two texts
Step 1: Paste both versions
Put the original on one side and the changed version on the other in the diff checker.
Step 2: Read the differences
Added text is highlighted one way and removed text another, line by line and word by word, so changes jump out.
Step 3: Review and act
Read the changes, copy whichever side you want to keep, and decide what to accept.
Line diff or word diff
A good diff works at two levels, and knowing which to read saves confusion:
- Line diff compares whole lines. If a line changed at all, the old version is marked removed and the new one added. This is ideal for code, config and lists, where lines are the natural unit and you want to see which ones moved or changed.
- Word diff looks inside a changed line and highlights only the words that differ. This is better for prose. If a sentence had one word swapped, a word diff shows just that word rather than flagging the whole sentence as changed.
For an edited paragraph, the word diff tells you the real story. For a changed config file, the line diff is clearer. Seeing both means small edits and large rewrites are equally easy to read.
Reading the results well
A couple of habits make a diff more useful. Compare like with like: if one version has different line breaks from the other purely because of how it was pasted, the diff will flag lines as changed when only the wrapping differs. Tidying both sides to a consistent structure first gives a cleaner comparison. And start from the biggest changes. A diff often shows a mix of trivial and significant edits; scan for the substantive ones first, then confirm the small ones are harmless.
Why local matters for sensitive text
Contracts, unreleased copy and private code are exactly the kind of text people compare, and exactly the kind you should not paste into a server you do not control. Running the comparison on your own device means both versions stay on your machine. Nothing is uploaded, so a sensitive document never leaves your hands just to be diffed.
Editing after you compare
Once you have spotted what changed, you may want to apply a consistent edit across the text, like reverting a renamed term everywhere. That is a find and replace job. See how to find and replace text in bulk.