Text Diff

How the Text Diff works

The tool compares the two texts line by line with the Myers diff algorithm, the same approach used by git diff and GNU diff. It finds the smallest set of added and removed lines that turns the original into the changed text, so moved or edited lines are matched up with as little noise as possible. Each side can have up to 20,000 lines; for texts that are completely different, the comparison stops after a few seconds and shows the differing part as replaced rather than freezing the page.

When a removed line is followed by an added line, the pair is shown as a change and compared again word by word, so you can see exactly which words, numbers or punctuation marks changed. Ignore case treats upper and lower case as equal, and Ignore whitespace ignores all spaces and tabs, like diff -w. Unchanged lines more than three lines away from a change are folded unless you tick Show all unchanged lines.

The unified diff at the bottom uses the standard format with --- and +++ headers and @ hunks with three lines of context, so you can paste it into a code review, an issue or a patch tool. If the last line of a text has no line break after it and appears in a hunk, the line \ No newline at end of file is added, as diff does.

How to use the Text Diff

1. Paste the original text into the Original text box and the new version into the Changed text box, or open a file for each. Select Load example to try it.
2. Choose the View (Side by side or Inline) and, if needed, tick Ignore case, Ignore whitespace or Show all unchanged lines.
3. Select Compare or press Ctrl + Enter. Added lines are shown in green, removed lines in red, and the words that changed inside a line are highlighted.
4. Copy the unified diff or download it as a .diff file to share the changes.

Example

Comparing the original:

host = localhost
port = 8080
debug = true

with the changed text:

host = localhost
port = 9090
debug = false
timeout = 30

reports 3 added, 2 removed and 1 unchanged line, highlights 8080 → 9090 and true → false inside the changed lines, and produces this unified diff:

--- original
+++ changed
@@ -1,3 +1,4 @@
 host = localhost
-port = 8080
-debug = true
+port = 9090
+debug = false
+timeout = 30

Common use cases

• Reviewing what an editor or colleague changed in a document or contract.
• Comparing two versions of a configuration file before a deployment.
• Checking the differences between two SQL queries, API responses or code snippets.
• Creating a unified diff to paste into a bug report or code review.

Frequently asked questions