Compare two texts and see what changed
Paste two versions and get a line-by-line report of what was added and removed. Free, no account, and the comparison runs in your browser, not on a server.
How it works
Both texts are split into lines on any of the three line endings, so a file written on Windows and one written on a Mac are not reported as entirely different documents. The longest sequence of lines common to both is then found by filling a table of one side against the other, and walking that table produces the report: lines in the common sequence are unchanged, everything left on one side was removed, everything left on the other was added.
What to watch out for
Changing a single word reports the line as removed and its replacement as added, rather than highlighting the word. That is the same convention version control uses, and it is what makes the output readable in a plain text file — but for comparing two long paragraphs of prose it is coarser than a word-level comparison would be.
Nothing here tracks a block that has travelled. Text cut from one place and pasted into another appears twice in the report, once as removed and once as added, with no note that they are the same words. Reading the two together is the only way to tell a move from a rewrite.
Finding the longest common subsequence fills a table of one side by the other. Two texts of two thousand lines is sixteen megabytes and finishes instantly; two of a hundred thousand would ask for something close to eighty gigabytes and take the browser tab down with it. Beyond the limit the tool refuses rather than trying.
Limits
Files up to about 5 MB work reliably. Beyond that, the ceiling is your device's memory rather than any rule we impose — the work happens on your own machine. Tested in Chrome 140, Firefox 143, Safari 18.
Two versions and no idea what moved
Somebody sends back a paragraph “with a couple of small changes”. A configuration file stops working after an edit nobody remembers making. Two copies of the same licence differ somewhere, and the difference matters.
Reading both and spotting it by eye is unreliable in a way that gets worse the more similar the texts are. This does the comparison mechanically: every line is either in both, only in the first, or only in the second.
What the report looks like
Lines that were removed are marked with a minus, lines that were added with a plus, and unchanged lines around them carry a space. It is the same shape that version control has used for decades, which means it needs no explanation to anybody who has seen a code review and very little to anybody who has not.
Between changes, runs of untouched text are summarised as a count rather than repeated. A report that reproduces both documents in full is not a report, and when two contracts differ in one clause the ninety unchanged pages are not the interesting part.
The two switches
Ignoring capitalisation and ignoring spacing both relax what counts as the same line. They are worth reaching for when one side has been through a word processor that reformatted it, or when comparing something indented differently.
The text kept in the report is always the original, spacing and all. The comparison is relaxed; the output is not a rewrite of what you pasted.
Nothing is sent anywhere
Both texts stay in this tab. That matters more than it sounds for this particular tool — the things people compare are draft contracts, credentials, configuration files and half-finished writing, which is exactly the category nobody should be pasting into a form that posts it to a server.
Your files never leave your browser. Last updated 2026-08-07.
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