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Castov
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Diff Checker

Compare two versions of code, configuration files, or prose side by side. Highlights additions, deletions, and modifications line by line without sending any data over the network.

Diff Checker

Compare text or code line by line to see what changed.

Original Text

Modified Text

Diff Result

function hello() {
- console.log('world');
+ console.log('world!');
}

Fast In-Browser Text and Code Comparison

Spotting subtle changes between two versions of an API response, JSON configuration, or code snippet can be difficult with the naked eye.

Our client-side diff checker uses an optimized longest common subsequence algorithm to highlight exact line additions and deletions instantly.

Want the background? Read our comprehensive guide: Understanding Diff Algorithms and Patch Workflows.

How to use this tool

  1. Paste the original version of your text into the left pane.
  2. Paste the modified version into the right pane.
  3. Examine the highlighted line-by-line diff with color-coded additions and removals.
  4. Copy the diff or share the comparison URL.

Examples

Line by line code comparison.

Configuration Change

Original: port=3000 -> Modified: port=8080

Change
Modified port number line

Frequently Asked Questions

Is the text sent to any remote server?
No. The diff algorithm executes entirely inside your browser sandbox.
Does this support code as well as plain text?
Yes, it works identically for code files (JavaScript, Python, JSON, YAML) and plain text documents.
How are additions and deletions displayed?
Additions are highlighted in green, deletions in red, and unchanged lines in muted neutral tones.
Can I share the comparison with a teammate?
Yes, click Share to encode the state into the URL hash without storing anything on a server.

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