Diff Checker
Compare two blocks of text and see the differences line by line.
Runs entirely in your browser — your data never leaves this page.
About the Diff Checker
This diff checker compares two blocks of text and highlights exactly what was added and removed, line by line. It uses a longest-common-subsequence algorithm — the same core idea behind git diff — to find the smallest set of changes between the original and the changed version.
Paste two versions of a file, config, or paragraph to instantly see the differences, with added lines marked in green and removed lines in red. Everything runs locally, so you can compare private code or documents safely.
How to use it
- 1Paste the original text into the left panel.
- 2Paste the changed text into the right panel.
- 3Review the line-by-line differences below, with additions and removals color-coded.
- 4Use the +/− counts to see the size of the change at a glance.
Common use cases
- Comparing two versions of a config or code file
- Reviewing edits to a document
- Spotting what changed in an API response
- Checking differences before a copy-paste
Frequently asked questions
Is the comparison line-based or character-based?
This tool compares text line by line, which is ideal for code, config files, and structured text. Whole lines are marked as added or removed rather than highlighting individual characters within a line.
Is my text uploaded anywhere?
No. The diff is computed entirely in your browser, so you can safely compare private code, credentials, or confidential documents.
Can it compare JSON or code?
Yes. Any plain text works, including JSON, source code, CSV, and logs. For JSON, formatting both sides first (with the JSON Formatter) produces the cleanest, most readable diff.