Free tool · nothing leaves your browser

Diff checker

Paste the original on the left and the changed version on the right. You see what was removed, what was added, and which words changed. Your text never leaves your device.

How to use it

  1. Paste the original text on the left and the changed version on the right. You can also drop a text file onto either box, or press Open file.
  2. Press Find difference (or Ctrl+Enter, Cmd+Enter on a Mac). Red marks what was removed from the original and green marks what was added.
  3. Choose how to look at it. Split puts the two versions side by side, Unified shows one column with removals above additions, which suits a phone. Highlight inside lines marks the changed words, or the changed letters, within a line that was edited.
  4. Take it with you. Copy diff and Download .diff give you the changes in the standard unified format that git apply and patch understand.

What comes out

These two short texts were run through the same code your browser uses:

The quick brown fox jumps over the lazy dog.
It was a bright cold day in April.
All clocks were striking thirteen.
Winston slipped quickly through the glass doors.
The quick brown fox leaps over the lazy dog.
It was a bright cold day in April.
All the clocks were striking thirteen.
A new line was added here.
Winston slipped quickly through the glass doors.

The unified diff is:

--- original
+++ changed
@@ -1,4 +1,5 @@
-The quick brown fox jumps over the lazy dog.
+The quick brown fox leaps over the lazy dog.
 It was a bright cold day in April.
-All clocks were striking thirteen.
+All the clocks were striking thirteen.
+A new line was added here.
 Winston slipped quickly through the glass doors.

Lines starting with - were removed, lines starting with + were added, and lines starting with a space are unchanged context. A changed line is shown as a removal followed by an addition, and the checker marks the words that differ inside the pair.

The options

  • Ignore whitespace treats extra spaces, tabs and trailing spaces as nothing, so a re-indented paragraph does not light up. Line breaks still count.
  • Ignore case treats Hello and hello as the same.
  • Swap flips the two boxes, which turns additions into removals.
  • Hide unchanged lines folds long unchanged stretches down to three lines of context either side of a change, with a button to open each fold. It switches on by itself for very long texts.
  • Prev and Next jump from one change to the next.

Your text stays on your device

Most online compare tools send what you paste to their server. This one cannot: the comparison is done by the page itself, in your browser's memory. There is no upload, no saved copy and no log of what you compared, so it is safe for contracts, code, drafts and anything else you would not paste into someone else's website. Switch your network off after the page loads and it still works.

How big can it be?

Ten thousand lines compare in well under a second. Big comparisons run in the background so the page stays responsive. Files up to 8 MB can be opened. Anything much larger is better handled by a command-line tool.

Common questions

Does it compare by line, by word or by letter?

By line first, because that is how people think about changes to text and code. Inside a line that was edited it then marks the changed words, or the changed characters if you pick Characters.

Why do some changed lines have no highlights inside?

If the old and new line share nothing at all, the whole line is the change, and marking every word would add nothing. Lines that share even a single word get the detailed marks.

Can it compare two files?

Yes. Open or drop a text file into each box. Plain text, code, markdown, CSV, JSON and logs all work. PDFs and Word files are not plain text: convert a PDF with our PDF to markdown converter first and compare the result.

What is the unified format?

It is the change format used by diff -u and by Git: a header naming the two versions, then hunks that begin with an @@ line giving the line ranges, followed by the changed lines with three lines of context.

Is it free?

Yes, with no account, no limit and no watermark.

While you are here

The rest of Final Boss Games is daily puzzles and small browser games. The other tools here, like the word search generator, follow the same rule: free, no sign-up, and nothing you type leaves your browser.