What is the Text Diff Checker?

A free online tool that compares two texts side by side, highlighting additions in green and removals in red. It also shows how many lines were added, removed or unchanged and lets you copy the diff in the standard unified format with + and - prefixes.

How does the online text comparison work?

Paste the original text into the left field and the modified version into the right one, then click Compare. The algorithm splits the texts into lines, computes the Longest Common Subsequence and renders the difference with colors in a side-by-side table, including line numbers.

Are my texts sent to any server?

No. The full comparison happens inside your browser, in JavaScript. Nothing is uploaded to ToolboxHub servers, which makes the tool safe to review sensitive content such as contracts, personal data or proprietary code.

Can I compare long texts?

Yes. The diff checker supports texts with thousands of lines. Since the work is done in your browser, performance depends on the device memory. For very large files, comparing chunks at a time gives a faster response.

Which algorithm is used?

The diff checker uses the LCS (Longest Common Subsequence) algorithm over the lines of both texts. It is the same principle adopted by Unix diff and tools like git diff: it identifies the longest shared sequence of lines and marks the rest as added or removed.

Can I compare source code snippets?

Yes. The comparison is line by line and works well with any language (JavaScript, Python, Java, PHP, SQL, etc.). To avoid differences caused by indentation, enable the "Ignore whitespace" option and the diff checker will strip leading and trailing spaces on each line.

How do I copy the resulting diff?

After comparing, click the "Copy diff" button at the top of the result. The text is copied in the unified format, with each removed line prefixed by "- ", each added line by "+ " and unchanged lines with two spaces, the same convention used by Unix patches.

What do the ignore case and ignore whitespace options do?

"Ignore case" treats uppercase and lowercase letters as the same, useful when texts have inconsistent capitalization. "Ignore whitespace" removes leading and trailing spaces on each line before comparing, helpful when the only differences are indentation or invisible spaces.

Free Online Text Diff Checker: Compare 2 Texts Side by Side

About the Text Diff Checker

The Text Diff Checker is a free tool that finds differences between two pieces of text, showing additions, removals and unchanged lines in a side-by-side layout. Internally it uses the LCS (Longest Common Subsequence) algorithm, the same principle behind tools like git diff. It is useful for reviewing contracts, checking article revisions, comparing code snippets and validating changes in any textual content.

How to compare texts in 5 steps

Paste the original text into the left field.
Paste the modified text into the right field.
Toggle Ignore case or Ignore whitespace if needed.
Click Compare to see the side-by-side diff with colored highlights.
Copy the result, swap the texts to inspect the opposite direction, or clear everything for a new comparison.

When to use the Text Diff Checker

Document review: spot edits in contracts, proposals and articles before signing off.
Version checking: compare a delivered draft with the revised version from another reviewer.
Source code comparison: quickly visualize changes in scripts, configs and snippets before committing.
Translation review: cross-check an original text against its translation to find missing segments.
Email and contract audit: find clauses changed in replies and revisions.
Data migration validation: compare dumps, logs or database exports to detect divergences.

Text diff checker features

Side-by-side comparison in two columns
Color highlighting: red for removals and green for additions
Line numbering on both texts
Optional case-insensitive comparison
Optional whitespace-insensitive comparison
Stats for added, removed and unchanged lines
Copy diff in the standard unified format with + and - prefixes
100% in-browser processing — no text is sent to any server

Text Diff Checker