OnliKit

Diff Checker

Compare two text blocks with inline red and green highlights

Use Diff Checker free in your browser. Free online diff checker. Paste two text blocks and see line-by-line differences with red removed lines, green added lines, line numbers, and copy or download support — no signup.

Loading tool…

What you can do with Diff Checker

Diff Checker on OnliKit is a free browser tool for everyday work — compare two text blocks with inline red and green highlights. Use it when you need a quick result without installing software or creating an account.

  • Paste two text blocks and compare them instantly in the browser.
  • See removed lines in red and added lines in green with line numbers.
  • Keep the original and updated text visible side by side while reviewing the diff.
  • Copy the diff output or download it as a text file.
  • Swap the left and right inputs to reverse the comparison quickly.
  • All comparison happens locally in your browser for privacy.

Why use Diff Checker?

Use Diff Checker when you need a quick before-and-after review for text, code snippets, notes, generated output, or config changes. The workspace keeps both inputs visible and renders a readable inline diff below them.

Because the diff runs on your device, you can compare sensitive text without uploading it to an external service. It is especially handy for checking edited prompts, copied logs, small config files, or manually reviewed content updates.

How to use Diff Checker

  1. 01Paste the original text into Text A and the updated text into Text B.
  2. 02Review the highlighted diff output below the inputs.
  3. 03Use Swap if you want to reverse the comparison direction.
  4. 04Copy or download the diff when you are done.

Frequently asked questions

Does the diff checker upload my text?

No. The comparison runs entirely in your browser, so your text is not uploaded to OnliKit servers.

How are additions and removals shown?

Added lines are highlighted in green and removed lines are highlighted in red. Unchanged lines stay neutral so the edits stand out.

Can I compare code as well as plain text?

Yes. The tool works for any line-based text, including code snippets, logs, notes, prompts, and config files.

Is this a side-by-side diff tool?

The inputs are side by side so you can review both versions at once, while the result panel shows a single readable line-by-line diff with colors and line numbers.

Related tools

After you finish with Diff Checker, try these related OnliKit tools — or browse all tools.

Also see more data tools.