What is a diff checker?
A diff checker compares two texts and shows which lines were added, removed or changed. It is the same idea as diff on the command line or the changes view in Git, without installing anything. Paste the original on the left and the new version on the right; the differences are marked immediately, and inside each changed line the exact words that differ are highlighted, so a single changed digit in a long line is easy to spot.
How to compare two texts
- Paste or drop the original text on the left and the changed text on the right.
- The comparison runs as you type; the summary shows how many lines changed, were added and were removed.
- Tick Ignore whitespace if indentation or spacing changes should not count.
- Keep Hide identical lines on to collapse unchanged parts, and use Previous / Next to jump between changes.
Reading the result
| Colour | Meaning |
|---|---|
| Red background on the left | Line removed or replaced; darker red marks the removed words |
| Green background on the right | Line added or replacement line; darker green marks the new words |
| Striped cell | No corresponding line on that side |
| Light yellow | Lines equal only because whitespace is ignored |
| Grey bar | Collapsed identical lines; click to expand |
Common uses
- Code review without Git: compare two versions of a function or a config snippet from a chat or ticket.
- Documents and contracts: find what an edited paragraph actually changed.
- Logs and outputs: compare the output of a working and a failing run.
- Data files: spot changed rows in CSV exports.
Structured data
A line-based diff treats JSON and YAML as plain text, so reordered keys or re-indented blocks show up as changes. For those formats use the JSON diff or the YAML diff, which compare the data itself and list changed paths.