Diff Checker
Compare two blocks of text and see added and removed lines.
ToolsSoup's Diff Checker is a free online tool that compares two blocks of text and highlights exactly what changed. Paste an original version on the left and an edited version on the right, then click Compare to see a clear line-by-line diff with added lines in green and removed lines in red. Everything runs in your browser — your text is never uploaded, so it is safe for code, contracts, and private notes alike.
What is a diff checker?
A diff checker — also called a text comparison or text difference tool — takes two versions of a document and shows you what was added, removed, or left unchanged. It compares the two inputs line by line using a longest-common-subsequence algorithm, the same approach version-control systems use, so matching lines stay aligned and only the real edits are flagged. Developers use it to review code changes, while writers and editors use it to track revisions between drafts.
How to compare two texts online
Checking the difference between two texts with ToolsSoup takes just a few seconds:
- Paste the original text into the box on the left.
- Paste the changed text into the box on the right.
- Optionally enable Ignore case or Ignore whitespace to skip cosmetic-only differences.
- Click Compare to see added lines in green and removed lines in red, with a count of each.
- Click Copy diff to copy the result, using plus and minus prefixes per line.
What do the colors and symbols mean?
Removed lines that exist only in the original are shown in red with a minus prefix. Added lines that exist only in the changed text are shown in green with a plus prefix. Unchanged lines that appear in both are shown in gray with no marker, so you can read the edits in context. A summary above the result tells you how many lines were added and removed.
Why use this diff checker?
- 100% free with no ads, sign-up, or usage limits.
- Runs entirely in your browser — your text is never uploaded to a server.
- Line-by-line comparison that keeps matching lines aligned.
- Optional ignore-case and ignore-whitespace modes for cleaner results.
- Copy the full diff with plus and minus prefixes in one click.
Frequently asked questions
Is this diff checker free?
Yes. Every tool on ToolsSoup is completely free to use, with no account, sign-up, or hidden limits.
Is my text safe?
Absolutely. All comparison happens locally in your browser using JavaScript, so neither version of your text is ever sent to or stored on any server.
Can I compare source code with this tool?
Yes. The diff checker compares any plain text line by line, which makes it well suited for code, configuration files, logs, and documents alike.
What is the difference between ignore case and ignore whitespace?
Ignore case treats uppercase and lowercase letters as the same, so 'Hello' and 'hello' match. Ignore whitespace collapses runs of spaces and tabs and trims line ends, so lines that differ only in indentation or spacing are treated as identical.
Does the tool compare line by line or character by character?
It compares line by line. Whole lines are matched against each other, so a line is reported as either unchanged, added, or removed rather than highlighting individual characters within a line.