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Diff Checker

Paste the original on the left and the new version on the right. Added lines are marked +, removed lines −, and inside a reworded line the exact words that changed are highlighted — so a one-word edit to a contract clause or a config value does not hide in a wall of text.

Show

Paste two versions of a text to see what changed.

How to use this tool

  1. Paste the original text into the first box and the changed version into the second.
  2. Read the summary: how many lines were added, removed and left alone.
  3. Scroll the comparison. Removed lines are red and marked −, added lines green and marked +, and changed words inside a line are highlighted.
  4. Tick “Ignore spacing” or “Ignore upper and lower case” when those differences do not matter to you.
  5. Choose “Changes only” to fold away long unchanged stretches and keep two lines of context around each change.

Formula and method

How lines are matched

changes = (lines in A − shared lines) + (lines in B − shared lines)

The tool finds the longest sequence of lines the two texts share, in order, using Myers’ algorithm — the one git uses. Everything outside that shared sequence is reported as removed or added, which is the smallest set of changes that turns one text into the other.

Worked examples

A price changed in one line

  1. Original: “The fee is 500 rupees.”
  2. Changed: “The fee is 750 rupees.”

One line removed and one added, with only “500” and “750” highlighted inside them.

Notes and limitations

  • Everything runs in your browser. Neither text is uploaded or stored, so drafts, contracts and configuration files stay on your device.
  • Comparison is line by line. A paragraph written as one long line counts as one line, though the changed words inside it are still highlighted.
  • Within each block of changes, removed and added lines are paired in order for word highlighting. When a block removes three lines and adds two, the third removed line is shown without a partner.
  • Windows (CRLF) and Unix (LF) line endings are treated the same, so a file saved on another system does not show every line as changed.
  • Texts that differ in more than about 4,000 lines are not compared line by line — at that point they are different documents rather than versions of one.

Frequently asked questions

Is it safe to compare confidential documents here?

Yes. The comparison is done by JavaScript in your browser and nothing is sent to a server. You can disconnect from the internet after the page loads and it still works.

Can I compare two files?

Open each file in a text editor, copy its contents and paste them into the two boxes. Code, CSV, JSON, Markdown and plain text all work. Word and PDF files need their text copied out first.

Why does a line I did not change show as different?

Usually because of invisible differences: a trailing space, a tab instead of spaces, or a curly quote instead of a straight one. Tick “Ignore spacing” to rule out the first two.

Is this the same as git diff?

It uses the same algorithm to match lines, so the changes it reports are the ones git would show. It adds word-level highlighting inside changed lines, which git shows only with --word-diff.

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