Is my text uploaded anywhere?

No. The comparison runs entirely in your browser with JavaScript, so neither block of text ever leaves your device or touches a server.

How does the diff work?

It compares the two texts line by line using a longest-common-subsequence algorithm. Lines only in the original are marked removed, lines only in the changed version are marked added, and matching lines are shown unchanged.

Can I ignore case or whitespace?

Yes. Tick "Ignore case" to treat upper and lower case as equal, or "Ignore leading/trailing spaces" so indentation and trailing spaces do not count as differences.

Text Diff Checker — Compare Two Texts Online

Text Diff Checker

Paste two versions of any text and instantly see what changed — added lines in green,removed lines in red, and a tally of additions and deletions, all100% in your browser.

Original

Changed

Ignore case Ignore leading/trailing spaces

Diff result

🔒 100% private — runs in your browser, never uploaded.

How to compare two texts

Paste the first version into the Original box.
Paste the second version into the Changed box.
Optionally tick Ignore case or Ignore leading/trailing spaces so cosmetic differences do not show up.
Click Compare. The result fills in below: green + lines were added, red - lines were removed, and plain lines are unchanged.
Read the counts at the top, then press Copy diff to grab a plain-text version with +, - and space prefixes.

How the line diff works

Under the hood the tool runs a classic longest-common-subsequence (LCS) diff over the lines of your two texts — the same idea behind the diffs you see in Git and code review tools. It finds the longest set of lines that appear, in order, in both versions, and treats everything else as an edit. Lines that exist only in the Original are reported as removed, lines that exist only in the Changedtext are reported as added, and the shared backbone is shown as unchanged. Because it works on whole lines, moving a paragraph shows up as one block removed and one block added, which is usually exactly how you want to read a revision.

When a text diff is handy

A line-based diff is perfect for spotting edits between two drafts of an email, contract or article, checking what a teammate changed in a config file or list, confirming a copy-paste came through intact, or reviewing the before-and-after of generated output. The addition and deletion counts give you a quick sense of how big a change is at a glance — a one-line tweak versus a wholesale rewrite — before you read a single line. Your original text stays in the input boxes, so you can toggle the case and whitespace options and compare again without losing anything.

Is it private?

Yes — the entire comparison happens in your browser with plain JavaScript. Neither block of text is ever sent to a server, stored or logged, and nobody else can see it. Once the page has loaded you can even run the tool completely offline. That makes it safe for comparing sensitive material like contracts, source code or private notes.

Frequently asked questions

Does it upload my text?

No, everything runs locally in your browser and nothing is transmitted or saved anywhere.

Does it diff word by word or line by line?

It compares whole lines. A change anywhere on a line marks that line as removed (from the original) and added (in the changed version).

What do the counts mean?

Added is the number of lines present only in the Changed text, Removed is the number present only in the Original, and Unchanged is the count of lines that matched in both.