Text Diff Checker
See exactly what changed between two versions of a text.
How to use the Text Diff Checker
- Paste the original text on the left and the changed version on the right, or open a file in each.
- Differences appear below as you type: removed lines in red, added lines in green, changed words highlighted inside each line.
- Switch between side-by-side and unified view, and ignore whitespace or letter case if those changes do not matter.
- Copy or save the result as a unified diff to share it.
About this tool
When two versions of a document, contract, config file or piece of code look almost the same, spotting what changed by eye is slow and unreliable. This diff checker lines the two texts up and marks every line that was removed, added or edited. Inside edited lines it goes one step further and highlights the exact words that changed, so a single altered number or a missing "not" is impossible to miss.
The comparison uses the Myers difference algorithm, the same approach behind git diff, which finds the smallest set of changes that turns one text into the other. It runs entirely in your browser and handles files of several thousand lines in a fraction of a second. Long unchanged stretches are folded away so you can focus on the edits; click a fold to expand it.
Tip: turn on "Ignore whitespace" when comparing code or text that was re-indented or has trailing spaces, and "Ignore case" when only capitalisation differs. The counters show how many lines were added and removed in total.
Frequently asked questions
What do the colours mean?
Red lines exist only in the original text and were removed. Green lines exist only in the changed text and were added. When a line was edited, it appears as a red and green pair, with the specific words that changed shaded more strongly.
What is the difference between side-by-side and unified view?
Side-by-side shows the original and changed text in two columns, which is easiest to read on a wide screen. Unified view shows a single column with removed lines marked − and added lines marked +, like git diff. It works better on phones and is what the copy and save buttons produce.
How large can the texts be?
Several thousand lines each compare almost instantly. Very large or completely different texts take longer because every line has to be matched, but everything still runs locally.
Are my texts uploaded or saved?
No. The comparison happens in your browser and nothing is sent anywhere. Both texts are kept only in this browser's local storage so they are still there if you reload; the Clear button removes them.