Diff Checker
Compare two blocks of text line-by-line and see exactly what was added, removed or kept. The diff is computed with a classic LCS algorithm — no libraries, no backend. Toggle case-sensitivity and whitespace normalisation to suit your workflow.
How to use
- 1
Paste the original text
Drop the before version of your text into the left-hand editor (for example, a draft commit message or an old API response).
- 2
Paste the changed text
Drop the after version into the right-hand editor. Anything you change will appear as a removed + added pair.
- 3
Tweak the options
Toggle Ignore case to treat Foo and foo as identical, or Normalise whitespace to collapse runs of spaces and trim trailing whitespace before comparing.
- 4
Compare and copy
Click Compare. Use the badges to see the number of additions and removals, and Copy diff to grab a unified-text version for a PR or chat.
Common use cases
- Review a config file change before committing it.
- Compare two API responses to spot what changed between deploys.
- Check whether a refactored function still produces the same output.
- Verify that two large text files are identical or see exactly where they differ.
Limitations
- The diff is line-based — intra-line character diffs are not highlighted.
- Inputs larger than 1 MB per side are rejected to keep the tab responsive.
- The LCS algorithm runs in O(n·m) time and memory, so very large files (tens of thousands of lines) will be slow.
Frequently asked questions
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