Text Compare (Diff Checker)
Compare two texts side by side and highlight every added, removed or changed line — a free online diff checker.
About the Text Compare (Diff Checker)
This free text compare tool (diff checker) finds the differences between two pieces of text instantly. Paste the original version on the left and the changed version on the right, and every added, removed and unchanged line is highlighted in a unified, color-coded view — additions in green-tinted highlight, deletions in red, unchanged lines dimmed for context.
Under the hood it uses the longest common subsequence (LCS) algorithm — the same approach behind Git and professional diff tools — so it correctly matches the lines the two texts share and isolates the real changes rather than flagging everything after the first difference. Counters above the diff summarise how many lines were added and removed.
Writers use it to see what an editor changed, developers use it to compare config files and code snippets without opening a terminal, and students use it to check drafts against revisions. Comparison happens entirely in your browser, so both texts stay private on your device.
How to Use the Text Compare (Diff Checker)
- 1Paste the original text in the left box.
- 2Paste the changed text in the right box.
- 3Read the color-coded diff: added lines highlighted, removed lines in red.
- 4Check the added/removed line counters for a quick summary.
Frequently Asked Questions
How do I compare two texts online for differences?
Paste the first version into the left box and the second into the right box — the diff appears automatically, no button needed. Lines present only in the second text are marked as added, lines only in the first as removed, and identical lines are shown dimmed so you can see the surrounding context.
Does this diff checker compare word by word or line by line?
It compares line by line, like Git and classic diff utilities. A line counts as changed if any character on it differs, so a one-word edit shows the old line as removed and the new line as added. For prose, putting each sentence on its own line before comparing gives more precise results.
What algorithm does the text comparison use?
It uses the longest common subsequence (LCS) algorithm, the standard basis for diff tools. LCS finds the largest set of lines the two texts share in the same order, then marks everything outside that set as added or removed. This avoids the naive problem where a single inserted line makes everything after it look changed.
Can I compare code or configuration files?
Yes — the diff is rendered in a monospace font and preserves indentation, making it well suited to source code, JSON, YAML, .env files and SQL. Because whitespace is significant, lines differing only in indentation are reported as changed, which is usually exactly what you want when reviewing code.
Is the text I compare kept private?
Completely. Both texts are processed by JavaScript in your own browser and are never uploaded, stored or shared. You can safely compare contracts, unreleased articles or proprietary code — close the tab and the content is gone.