Diff Checker
Compare two blocks of text in your browser and see exactly what changed, line by line. Both panes have line numbers, added lines turn green and removed lines red, and you can ignore case or whitespace. Free, no signup, nothing uploaded.
How to use the diff checker
Paste the Original
Put the first version of your text into the left pane. Line numbers appear automatically.
Paste the Changed
Put the second version into the right pane. The differences highlight instantly.
Read the Highlights
Removed lines show red on the left, added lines green on the right, and the count shows how many changed.
Ignore What Does Not Matter
Turn on ignore case or ignore whitespace to focus only on the real content changes.
Spot Every Change at a Glance
Comparing two versions of something by eye is slow and unreliable. A moved line, a changed word, or an extra space is easy to miss when you are reading two blocks back and forth, and missing one can mean shipping the wrong version. This diff checker does the comparison for you and marks the changes right where they are.
What a diff checker does
A diff checker lines up two texts, works out which lines were added, removed, or kept the same, and highlights them so the changes are obvious. Here the two versions sit in side-by-side panes with line numbers. Removed lines are marked red on the left, added lines green on the right, and unchanged lines stay plain. It is the same line-by-line comparison developers call a diff, without installing anything.
How to compare two texts
Paste the original on the left and the changed version on the right. The highlighting updates as you type, so there is no compare button to press. Line numbers on both sides make it easy to point someone to an exact spot, and a running count at the top shows how many lines were added and removed.
What you can compare
The common jobs are reviewing a code change before it ships, checking what edits came back in a contract or a piece of writing, spotting a stray change between two config files, and proofreading two drafts of the same paragraph. Because it works on plain lines, it handles source code and ordinary prose the same way, from a two-line snippet to a few thousand lines per side.
Private by design
Everything runs in your browser with JavaScript. Your text is never uploaded, logged, or stored, which matters when you are comparing contracts, credentials, or unreleased code. Many online compare tools send your text to a server, and some even suggest an offline tool for sensitive content. Here the offline behavior is built in, so you can paste freely.
Ignore case and whitespace
Sometimes only the real content matters. Turn on ignore case and a line that changed only from Title to title is treated as unchanged. Turn on ignore whitespace and differences in spaces, tabs, or trailing blanks are skipped, so reformatting does not drown out the edits you actually care about.
Why Use Our Diff Checker?
Line-by-Line Diff
Two texts are lined up and compared line by line, so every added, removed, and unchanged line is clear.
Line Numbers
Both panes are numbered, so you can point to an exact line when you share what changed.
Added and Removed Color
Removed lines show red on the left and added lines green on the right, highlighted in place.
Ignore Case
Treat lines that differ only in capitalization as unchanged, so case noise does not hide real edits.
Ignore Whitespace
Skip differences in spaces, tabs, and trailing blanks so reformatting does not clutter the result.
Live as You Type
The comparison updates on every keystroke, with a running count of added and removed lines.
Code and Prose
Works the same on source code and plain text, from a couple of lines to a few thousand per side.
Runs in Your Browser
Your text is compared on your device. Nothing is uploaded, logged, or stored.
Similar Tools
More Developer tools you might find useful.
Frequently Asked Questions
Common questions about comparing text.
What is a diff checker?
A diff checker compares two versions of text and highlights what changed between them. It lines up the two versions, marks added and removed lines, and leaves unchanged lines plain, so you can spot every edit at a glance.
How do I compare two texts?
Paste the original into the left pane and the changed version into the right pane. The tool compares them line by line and highlights the differences instantly, with no compare button to press.
Does it show differences line by line?
Yes. Both panes have line numbers, and the comparison is line based. Removed lines are marked red on the left, added lines green on the right, and lines that match stay unhighlighted.
What do ignore case and ignore whitespace do?
Ignore case treats lines that differ only in capitalization as the same. Ignore whitespace skips differences in spaces, tabs, and trailing blanks. Both help you focus on real content changes instead of formatting noise.
Is my text uploaded anywhere?
No. The whole comparison runs in your browser on your own device. Nothing is uploaded, logged, or stored, so it is safe for contracts, credentials, and unreleased code that should not leave your machine.
Can I compare code?
Yes. The diff works on plain lines, so source code compares just as well as prose. It is handy for reviewing a change before it ships or spotting a stray edit between two config files.
How many lines can I compare?
You can compare up to about 5,000 lines per side and still get a fast result. Beyond that the comparison is capped to keep the tool responsive in the browser.
Is this diff checker free?
Yes, it is completely free with no signup and no limits on how many comparisons you run. Everything runs in your browser, so your text stays on your device.