Diff Checker
Compare two blocks of text line by line. Added lines show in green, removed lines in red. Everything runs in your browser, so your text never leaves your machine.
About the Diff Checker
The Diff Checker compares two blocks of text line by line and shows exactly what changed. Added lines are highlighted green, removed lines red, and unchanged lines stay plain. It is built for developers, writers, and WordPress users who need to spot edits between two versions of a file, a config snippet, a post draft, or any pasted text. Everything runs in your browser, so your text stays private and is never uploaded.
How it works
- Paste the original text in the left panel and the changed text in the right panel.
- Leave Live on to compare as you type, or turn it off and click Compare when you are ready.
- Read the result below: green lines were added, red lines were removed, plain lines are unchanged.
- Check the added and removed counts in the summary to see the size of the change.
Features
- Line-based comparison using a longest common subsequence algorithm for accurate matching.
- Color-coded output: green for additions, red for removals, plain for unchanged lines.
- Live mode that updates the diff as you type, with a manual Compare button when you prefer.
- Summary counts of added and removed lines.
- Swap sides, load a sample, and clear buttons for quick setup.
Frequently asked questions
Is my text uploaded anywhere?
No. The comparison runs entirely in your browser. Your text is never sent to a server or logged.
How does the line matching work?
The tool uses a longest common subsequence algorithm to find the largest set of lines shared by both versions. Lines outside that set are marked as removed from the original or added in the changed text.
Does it compare changes within a line?
The diff works at the line level. If one word in a line changes, the whole original line is shown as removed and the whole new line as added.
Does whitespace count?
Yes. Two lines must match exactly, including spaces, tabs, and trailing whitespace, to be treated as unchanged. A difference in indentation will mark the lines as changed.
Is there a size limit?
There is no fixed limit set by the tool. Because the comparison runs in your browser, very large inputs are limited only by your device's memory and may take longer to render.