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Code Diff Checker Online

Compare two versions of code with line-by-line highlighting. See additions, deletions, and modifications at a glance.

Text Diff Checker

Use this tool directly in your browser — no signup required.

Use Text Diff Checker

100% private — files are processed locally and never uploaded.

How to Code Diff Checker Online

  1. 1

    Paste the original code

    Put the old version of your code in the left panel. This is typically the last known working version.

  2. 2

    Paste the updated code

    Put the new version in the right panel. This might be the version with a suspected bug or the changes you want to review.

  3. 3

    Analyze the differences

    Walk through the highlighted changes line by line. Focus on red (removed) and green (added) sections to understand what was modified.

Debugging Starts with Knowing What Changed

"It was working yesterday." The fastest path to finding the bug is comparing yesterday's code with today's. If you don't have version control (or you're comparing outputs from two different systems), a diff checker gives you that comparison instantly.

This tool works for any programming language — it compares text, not syntax. JavaScript, Python, SQL, YAML, JSON, HTML, CSS — paste any two versions and see what's different. Line numbers in the output map to your original code so you can jump to the exact location in your editor.

Beyond debugging, code diffs are essential for code review. Before merging someone's changes, you want to see exactly what they modified. This is the same concept behind GitHub pull request diffs, just without needing a repository. Paste the before and after, review the changes, give feedback.

Frequently Asked Questions

Does this support syntax highlighting for specific languages?

The diff comparison itself is language-agnostic — it works on raw text. The highlighting shows additions, deletions, and changes, not language syntax. For syntax-highlighted diffs, you'd typically use an IDE plugin or GitHub.

Can I use this for minified code?

Technically yes, but the results won't be useful if everything is on one line. Run minified code through a formatter first (use our JSON formatter for JSON, or a code formatter for JS/CSS), then compare the formatted versions.

How is this different from the text compare tool?

Functionally, the diff engine is the same. This page is geared toward comparing code specifically, with context and tips relevant to developers. The text compare tool is oriented toward documents and general prose.