Text Diff
Paste two versions of a text and see exactly which lines changed.
Output
Paste or type above to see the result here.
Your files stay on your device
This tool runs entirely in your browser. What you paste is processed on your device and is never sent to a server, so it is safe to use with tokens, keys and unpublished text.
Example
Example: what changed between two versions of a tenancy summary
Version A is last year’s six-line summary of a tenancy. Version B is the renewal: new rent, new dates, a cat allowed and a line about the garden. A goes in the first box, B in the second; press Compare.
| Mark | Line | Meaning |
|---|---|---|
| (none) | Tenancy agreement, 14 Elm Road | The same in both |
| - | Rent: £1,150 per month | Only in A |
| + | Rent: £1,195 per month | Only in B |
| (none) | Deposit: £1,325 | The same in both |
| - | Term: 12 months from 1 March 2026 | Only in A |
| - | Pets: not allowed | Only in A |
| + | Term: 12 months from 1 March 2027 | Only in B |
| + | Pets: one cat allowed with written consent | Only in B |
| (none) | Bins: collected on Mondays | The same in both |
| + | Garden: tenant mows the lawn | Only in B |
The count says 4 added and 3 removed. Read the - and + lines as pairs: three lines were changed (rent, term, pets) and the garden line is new. Two changed lines in a row show both removals first, then both additions.
How it works
- Paste the original version into the main box (A).
- Paste the changed version into the second box (B) below it.
- The result appears as you type. The output is a unified diff: lines starting with - exist only in A, lines starting with + exist only in B, and unmarked lines are identical.
- Read through the changes. For configuration files or contracts, it is often easiest to look for + and - pairs, which show a line that was edited rather than added or removed.
Frequently asked questions
- Does the diff work by line, word or character?
- It is line-based, like git diff and the Unix diff command. A line that changed in a single character is shown as one removed line and one added line. Word-level highlighting inside a line is not applied yet.
- Which algorithm is used?
- A line-based longest-common-subsequence diff, the same idea git uses. It finds a shortest sequence of line insertions and deletions that turns A into B, so moved blocks appear as a deletion in one place and an insertion in another. Long unchanged runs are collapsed to keep the output readable.
- Are trailing spaces and line endings significant?
- Line endings are normalised, so a Windows CRLF file and a Unix LF file with the same content show no differences. Trailing spaces and tabs inside a line are significant, however, because they are real differences in the text.
- Why does a line I did not change show as removed and added?
- Something in it differs that is hard to see, most often a space at the end of the line or a different dash or quote mark: “b ” and “b” are different lines. Windows and Unix line endings, on the other hand, count as the same.
- What does “… unchanged lines …” mean?
- A run of more than six identical lines is shortened to its first three and its last three, with the number left out written in between, such as “… 12 unchanged lines …”.
- Can I compare two files?
- Open each file in a text editor, copy its contents and paste them into A and B. Each side can have up to 4,000 lines; a longer text is refused with a message, so compare it in parts.
- Is either text uploaded?
- No. The comparison runs entirely in your browser. You can compare draft contracts, source code with credentials, or private notes without anything leaving your device.
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