Code Diff Viewer — Compare Text and Code Side-by-Side
Paste two versions of any code file to instantly see what changed. Line-level diff with added, removed, and unchanged lines highlighted in green and red. Switch between side-by-side split view and unified diff view.
How to Use Code Diff Viewer — Compare Text and Code Side-by-Side
How to Use the Code Diff Viewer:
Paste Your Code: Enter the original version of the code in the "Original" textarea on the left and the modified version in the "Modified" textarea on the right. You can paste any plain text — JavaScript, TypeScript, Python, CSS, JSON, YAML, SQL, or any other language. The diff is computed instantly as you type or paste.
Load an Example: Click one of the example buttons (JS Function, Python Class, CSS Rules) to load a pre-built before/after pair and see the diff immediately. Use these to explore how the tool behaves before pasting your own code.
Read the Stats Bar: The bar below the inputs shows three counts: Added lines (green), Removed lines (red), and Unchanged lines (grey). This gives a quick summary of how much changed between the two versions.
Switch View Modes: Click the Split or Unified button to change how the diff is displayed.
- Split view shows the original on the left and the modified version on the right — great for seeing the full context of both versions simultaneously.
- Unified view shows all lines in a single column with + and − prefixes — exactly like the output of git diff.
Read the Diff Output: Added lines have a green background with a + prefix. Removed lines have a red background with a − prefix. Unchanged lines have no background. Line numbers are shown on both sides so you can locate changes in your editor quickly.
Copy the Diff: Click "Copy Diff" to copy the unified diff text to your clipboard. The output uses + and − prefixes and can be pasted directly into pull request descriptions, Slack messages, or documentation.
Common Use Cases:
- Code review prep: Quickly visualise what changed in a file before opening a pull request, without needing to run git diff in the terminal.
- Comparing config files: Paste two versions of a JSON, YAML, or .env file to spot configuration differences across environments (dev vs. prod, v1 vs. v2).
- Reviewing AI-generated code: Paste your original function next to an AI-suggested rewrite to see exactly what was changed before accepting it.
- Documentation diffs: Compare two versions of a README or changelog to confirm what was added or removed.
- Debugging regressions: When behaviour changed between two versions, diff the relevant source files to pinpoint the exact lines that differ.
Tips:
- The diff algorithm compares line by line — leading and trailing whitespace on each line is preserved, so indentation differences will appear as changed lines.
- If you want to ignore whitespace differences, normalise your code through a formatter (Prettier, Black, gofmt) before pasting.
- The tool supports up to 300 lines per file. For larger files, use git diff or a dedicated IDE diff tool.
- In split view, empty grey cells on one side indicate lines that exist only on the other side — they are placeholders to keep the alignment intact.
Frequently Asked Questions
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