Finding what changed between two versions of a document by reading both is slow and unreliable — the eye skips over small differences, which are exactly the ones that matter. A diff does the comparison mechanically and shows only what moved.
How to use the Text Diff Checker
- Paste the original text into the first box
- Paste the version you want to compare into the second
- Click Compare
- Read the highlighted result — green is added, red is removed
Reading a diff
- Green, prefixed + — lines present in the second text but not the first. Additions.
- Red, prefixed − — lines present in the first but not the second. Removals.
- Unmarked — identical in both.
An edited line normally shows as a removal immediately followed by an addition, because line-level diffing has no concept of a line being modified — only of one line disappearing and another appearing.
What a line diff will and will not catch
This compares whole lines. Change a single character and the entire line is flagged, which is correct but coarse: you still have to spot the character yourself.
It also means formatting changes can swamp the real differences. Re-wrapping a paragraph changes every line in it even when not a word has changed. If you are comparing prose, put each sentence on its own line first, and the diff becomes far more readable.
Frequently asked questions
Is my text uploaded to compare it?
No. The comparison runs entirely in your browser. Nothing is transmitted, so it is safe for contracts, credentials or unreleased code.
Why does one small edit show a whole line as changed?
This is a line-level diff — the unit of comparison is the line, so any change within a line marks the whole line. Character-level diffs are more precise but much noisier on real documents.
Can I compare two files rather than pasting?
Open each file, copy its contents, and paste. Direct file comparison is not supported here.
Does it ignore whitespace differences?
No — trailing spaces and changed indentation register as differences. That is often what you want when comparing code. For prose, normalise the whitespace first if it is creating noise.