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Text Diff Checker

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Compare two texts line by line - see exactly what changed, in your browser.

Free to use · No account needed

How to use

  1. Paste the original text on the left and the modified version on the right.
  2. The diff updates as you type - no button needed.
  3. Green = added, red = removed, plain = unchanged. Statistics show the totals.

Compare two texts or code files and see exactly what changed - additions, deletions and modifications highlighted line by line. Indispensable for reviewing code changes, proofreading document revisions, or verifying config edits before deploy.

Use cases

1. Use case: Review code changes Paste the old and new versions of a config or script to see exactly which lines were added or removed.

2. Use case: Compare document edits Track what changed between two drafts of an article or specification before approving it.

Practical tips

Paste complete versions of both texts — a missing paragraph at the start makes every following line show as changed. Watch for whitespace-only differences; they are real changes to a machine but invisible to you, which is exactly why the diff marks them. Use word-level reading for prose edits and line-level for code or lists. For contracts, diff the current draft against the last agreed version, not against memory. Like every tool on this site, the Text Diff runs entirely in your browser: the data you enter never leaves your device, nothing is uploaded to a server, and the tool keeps working if your connection drops.

Common mistakes

Diffs are honest, so the input has to be honest too:

  • Diffing against memory instead of a saved previous version — if you retype the original, the differences reflect your memory, not the real edits.
  • Ignoring whitespace-only changes; they are real to machines and scripts even when invisible to you.
  • Using line-level mode for prose edits, which marks a whole paragraph changed for a one-word fix — switch to word-level.
  • Pasting partial documents: a missing first paragraph makes every following line show as changed.

Frequently asked questions

Does the Text Diff send my data anywhere?

No. It runs entirely in your browser — your input is processed on your device and never uploaded. Refresh the page and it still works offline.

Why does the diff show a change where the text looks identical?
Almost certainly a whitespace difference: trailing spaces, tabs versus spaces, or different line endings (CRLF versus LF). Machines treat these as different characters, which is exactly why the diff marks them — and why whitespace display is worth enabling.
Can I diff two large files, like full documents or code files?
Yes — everything runs locally in your browser, so files of several megabytes generally work within your device's memory. Very large logs may be slow; trim the unrelated sections first and diff what matters.
How do I compare two texts?
Paste the original in the left box and the edited version in the right box. The diff updates live: green lines were added, red removed, unchanged shown in plain text.
What does the LCS algorithm mean?
The tool computes the Longest Common Subsequence of the two texts' lines, finding the minimal set of insertions and deletions to turn one text into the other - the same idea behind git diff.
Is my text uploaded anywhere?
No. The comparison runs entirely in your browser, so you can safely diff confidential code or drafts.

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