How to Use the Diff Checker

Our Diff Checker compares two text blocks and highlights the differences between them, similar to how Notepad++ or VS Code's built-in diff viewer works. This tool is essential for code reviews, debugging configuration changes, and tracking document revisions.

Paste your original text in the left panel. This is your baseline or "before" version.
Paste the modified text in the right panel. This is the "after" version you want to compare.
Click "Compare" to generate the diff. The tool analyzes both texts line-by-line and character-by-character.
Review the highlighted differences. Red indicates removed content, green shows additions, and amber highlights modifications.
Use navigation arrows (or Ctrl+↑/↓) to jump between differences quickly.

When to Use a Diff Checker

Code Reviews

Compare code changes before committing to version control. Spot unintended modifications and verify that only expected changes are included in your commits.

Configuration Debugging

When a working configuration breaks, compare the current version against a known-good backup to identify the problematic change quickly.

API Response Changes

Track changes in API responses over time. Compare expected vs actual JSON responses to debug integration issues.

Document Revision

Compare drafts of documentation, contracts, or any text content to track what changed between versions.

Understanding the Diff Algorithm

This diff checker uses the Myers diff algorithm—the same algorithm used by Git—to compute the minimum edit distance between two texts. The algorithm identifies the smallest set of insertions and deletions needed to transform the original text into the modified version.

For modified lines (where content exists in both versions but differs), the tool performs an additional word-level diff to highlight exactly which parts of each line changed. This character-level precision helps you spot subtle differences like typos, whitespace changes, or variable renaming.

Diff Options Explained

Sync Scroll: Keeps both panels scrolling together so corresponding lines stay aligned.
Ignore Whitespace: Treats lines as equal even if they differ only in spaces, tabs, or line endings.
Ignore Case: Performs case-insensitive comparison—"Hello" matches "hello".

Frequently Asked Questions

What file types can I compare?

Any plain text content works: code files, JSON, XML, CSV, Markdown, configuration files, or regular text documents. Binary files are not supported.

Is there a size limit for comparisons?

The tool handles files up to several thousand lines efficiently. Very large files (10,000+ lines) may take longer to process since all comparison happens in your browser.

Is my code sent to a server?

No. All diff computation happens locally in your browser using JavaScript. Your code never leaves your device, making this tool safe for sensitive or proprietary code.

What's the difference between this and Git diff?

This tool uses the same underlying algorithm as Git but provides a more visual, side-by-side comparison with character-level highlighting—making it easier to review changes without command-line tools.