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. The comparison happens automatically, with no Compare button: the algorithm splits the texts into lines, computes the Longest Common Subsequence and renders the difference with colors, line numbers and word-level highlighting.

Do I have to click a Compare button?

No. The comparison is recalculated automatically as you type or paste, running in the background so the interface never freezes. Change any option — ignore case, whitespace or blank lines — and the result updates instantly.

What is the difference between the side-by-side and unified views?

Side by side puts the original and the modified text in two synchronized columns, which works best for long texts and large rewrites. The unified view stacks removed lines (-) right above added lines (+) in a single column, like the output of git diff, which reads better on mobile and for small edits.

What does the highlight level do?

At line level the whole changed line is marked. At word level only the words that actually changed are highlighted inside the line, and at character level the highlight goes down to each letter — useful to spot a single swapped digit in a code, a date or an ID.

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 export the resulting diff?

Use the "Copy diff" button to send the result to the clipboard, or "Download .diff" to save it as a file. The text uses 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 options do?

"Ignore case" treats uppercase and lowercase letters as the same, useful when texts have inconsistent capitalization. "Ignore whitespace" normalizes spaces and indentation before comparing. "Ignore blank lines" drops empty lines, so a different number of line breaks no longer shows up as a difference.

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

1Paste the original text into the left field.
2Paste the modified text into the right field.
3Toggle Ignore case or Ignore whitespace if needed.
4Switch between the side by side and unified views and pick the highlight level: line, word or character.
5Hide the unchanged lines to focus on the differences, then copy the diff or download it as a .diff file.

Text Diff Checker