Text & Code Diff Checker

A diff lists what changed between two versions of a text: the lines that were removed, the lines that were added and the lines that stayed the same.

This tool compares the texts line by line. Removed and added lines at the same spot are paired as changed lines, and inside each pair the words that differ are highlighted.

What the options change

Ignore whitespace treats lines as equal when they differ only in trailing spaces, or in any spaces and tabs. Ignore case does the same for capital letters, and Ignore blank lines leaves empty lines out. Ignoring line endings is on by default: Windows ends lines with CRLF and Unix with LF, and the summary tells you when they differ.

Show only changes folds long unchanged stretches, keeping the context lines you choose around each change; click a fold to open it.

Reading a unified diff

The unified format is what git diff and diff -u print, and what you export here. Comparing this original with the changed version below it:

host: example.com
port: 8080
timeout: 30
retries: 3

host: example.com
port: 8443
timeout: 30
retries: 3
log: debug

gives this diff:

--- original
+++ changed
@@ -1,4 +1,5 @@
 host: example.com
-port: 8080
+port: 8443
 timeout: 30
 retries: 3
+log: debug

A space starts an unchanged line, - a removed one and + an added one. The header @@ -1,4 +1,5 @@ says the hunk starts at line 1 of the original and covers 4 of its lines, and starts at line 1 of the changed text and covers 5. When a last line has no line break, the diff adds the line \ No newline at end of file.

The export records every difference, even ones the options hide, so patch recreates the changed text exactly. It uses your context setting, 3 lines by default.

Limits

Each side can be up to 5 MB. Texts under 200,000 characters in total are compared as you type; larger ones when you press Compare, in a background worker you can cancel. The first 2,000 rows are drawn at once, and lines over 5,000 characters get no word highlighting.

Beyond 2,000 differences the result is simplified, with a notice: lines that occur once in each text are matched, and the rest is shown as removed and added blocks.

How to use

1. Paste the original on the left and the changed text on the right, or load a file on each side.
2. Read the summary, switch views, and step through with Next change.
3. Set the options, then copy the unified diff or download it as a .diff file.

Features

• Line-level comparison with Myers' diff algorithm, and word-level highlights in changed lines.
• Line numbers and - and + markers on every changed line, not colour alone.

Common uses

• Config files. See what changed in a settings file before you deploy it.
• API responses. Format both with the JSON Formatter first, with sorted keys, so key order doesn't show up as changes.
• Test output. Find the line where actual output stopped matching the expected output.
• Logs, code review and test data. Compare a passing run's log with a failing one, two versions of a snippet, or a fixture before and after.

Frequently asked questions