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Diff Checker

Compare two texts or code files and highlight differences

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Diff Checker compares two texts line by line using a real longest-common-subsequence algorithm — the same family of algorithm behind most code diff tools — to find the smallest set of additions and removals that explains the difference, rather than a naive line-by-line mismatch.

Diff Checker details

How to use Diff Checker

  1. 1

    Paste your original text on one side.

  2. 2

    Paste the changed text on the other side.

  3. 3

    Click "Compare" to see the diff.

  4. 4

    Review lines marked as same, added, or removed.

Everything you need to know about comparing text with a diff

What does a diff actually show?

A diff compares two versions of text and highlights exactly what changed — additions, deletions, and modifications — instead of you having to read both versions side by side and spot the differences manually.

When you actually need this

  • Comparing two drafts of a document to see what actually changed between them.
  • Reviewing a config file change before applying it, to spot unintended edits.
  • Checking two code snippets for subtle differences that are easy to miss by eye.

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Frequently Asked Questions

Does this compare word by word or line by line?

Line by line — each line is treated as a unit, so a single-character change inside a line still marks the whole line as changed.

Why does it find a different diff than I expected?

The algorithm finds the longest common subsequence between both texts, which gives the minimal set of changes — but when lines could align in more than one valid way, it may pick a different (still correct) alignment than you'd choose by eye.

What do "added" and "removed" mean exactly?

"Removed" marks a line present in the first text but not the second; "added" marks a line present in the second but not the first. Lines present in both, in the same relative order, are marked "same".

Does this tool send my text to a server?

Yes — both texts are sent to our servers to compute the diff and the result is returned to you; nothing is stored.

Is this tool free to use?

Yes — completely free, with no signup and no usage limits for casual use.