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Text Diff Checker

Compare two blocks of text and see exactly what was added, removed or left alone — line by line, side by side or unified. Both texts stay in your browser.

Original

Changed

About this text diff checker

A free diff tool that compares two blocks of text and shows exactly what changed. Paste an old and a new version and every line is marked as added, removed or untouched — side by side or as a single unified list — so you can spot an edit in a contract, an email or a block of code without reading both copies.

How it works

  1. 1
    Paste both versions

    Original on the left, changed version on the right. The comparison updates as you type.

  2. 2
    Choose a view

    Side by side lines the two texts up; unified puts everything in one column with + and − markers.

  3. 3
    Tune the matching

    Ignore case or ignore whitespace when reformatting shouldn't count as a change.

  4. 4
    Read the result

    Added lines are green, removed lines red, and a summary counts each so you know the size of the change.

Privacy

Both texts are compared in your browser and never uploaded, which matters when you are diffing a contract, a private message or unreleased code. Your drafts are kept only in your own browser storage.

Need to count what you wrote instead? Open the Word Counter.

Frequently asked questions

How does the comparison work?
It finds the longest common sequence of lines between the two texts, so unchanged blocks stay aligned and only genuine insertions and deletions are highlighted — the same approach version control uses.
What is the difference between the two views?
Side by side shows the original and the changed text in two aligned columns, which is easiest for reviewing. Unified stacks everything into one column with + and − markers, which is closer to a patch file.
Can it ignore formatting changes?
Yes. Turn on 'ignore whitespace' so re-wrapping or re-indenting doesn't register, and 'ignore case' so capitalisation alone isn't treated as an edit.
Is there a size limit?
Comparison is capped at 2,000 lines per side. The algorithm compares every line against every other, so anything much larger would freeze the page rather than finish.

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