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Code Diff Viewer — Compare Two Code Files Side by Side

Perform side-by-side textual comparisons to easily spot differences between two versions of code or text.

Inputs
Paste two versions to compare. Diff runs locally in your browser.
+2-1
Diff
1
line 1
2
-
line 2
3
line 3
4
1
line 1
2
+
line two
3
line 3
4
+
line 4
5
Note: This is a fast line-based diff intended for tool usage. For semantic diffs, we can add an advanced mode later.
Privacy note: All processing happens entirely in your browser. No data is sent to our servers.

About this tool

The Code Diff Viewer compares two versions of any text or code and highlights the differences. Additions are shown in green, deletions in red, and unchanged lines in grey — exactly like a GitHub pull request diff, but without needing Git or any account.

Works with any programming language, configuration file, SQL query, JSON, HTML, CSS, or plain text. Useful for reviewing changes between file versions, comparing API responses, or spotting differences in configuration.

Common use cases

  • Reviewing pull request snippets offline
  • Comparing environment configs
  • Comparing API responses side by side
  • Checking generated code against hand-written baseline

How to use

  1. Paste the original (old) version of your code into the left panel.
  2. Paste the modified (new) version into the right panel.
  3. The diff highlights automatically — green lines are additions, red lines are deletions, grey lines are unchanged.
  4. Use line-by-line or side-by-side view depending on your preference.

This page is available at /tools/code-diff-viewer/.

Understanding the result

  • Added lines (green): exist in the new version but not the old.
  • Removed lines (red): exist in the old version but not the new.
  • Unchanged lines (grey): identical in both versions.
  • Modified lines appear as a deletion of the old line plus an addition of the new line. The diff algorithm (usually Myers diff) finds the minimum number of changes that transform the original into the new version.

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FAQ

What file types can I compare?

Any plain text format — JavaScript, TypeScript, Python, Java, C#, PHP, HTML, CSS, SQL, JSON, YAML, XML, Markdown, or plain text. The tool compares raw text content, not compiled or rendered output.

Can I compare two entire files?

Yes. Copy the full contents of each file and paste into the respective panels. There is no size limit enforced by the tool itself, though very large files (10,000+ lines) may slow down the browser.

How is this different from Git diff?

Git diff compares file versions tracked in a repository. This tool compares any two text inputs with no Git required — useful for comparing text from different sources, different systems, or when you don't have Git access.

Are the code contents I paste stored anywhere?

No. All processing happens in your browser. Your code is never sent to any server.