Diff Shuttle

Compare Code Online Free — Line-by-Line Source Code Diff Checker for Any Language

Code Diff Tool

Compare two code snippets or source files online and see exactly what changed. Paste or upload both versions and get a clear, color-coded, line-by-line diff for any language — JavaScript, TypeScript, Python, Java, Go, Rust, C, C++, PHP, Ruby, SQL, and dozens more. Free, instant, and fully private, because everything runs in your browser.

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How to Compare Code

  1. 1

    Add Your Two Versions of the Code

    Paste the original code into the left box and the modified code into the right box. If your code lives in a file, use the Select File button or drag and drop a supported source file such as .js, .ts, .py, .java, .go, .rs, .php, or .sql onto either side. Files are read locally up to 10 MB each, and nothing is uploaded anywhere.

  2. 2

    Choose View and Options

    Keep the default line-by-line Text Diff mode, which is exactly what code review needs, and pick Side by Side to read both files in parallel or Unified for a compact patch-style view. Turn on Ignore Whitespace so a reformat or reindent does not bury the real logic change, and use Ignore Case for case-insensitive comparison when that matters.

  3. 3

    Review and Export

    Read the highlighted output, where added lines appear in green, removed lines in red, and unchanged lines stay neutral, each with its old and new line numbers. Check the statistics panel for additions, deletions, and the difference percentage, then click Export as Text to download a patch-style report for a pull request, code review, or commit note.

Why Use a Code Diff Tool?

See Every Logic Change

Reading two versions of a function by eye is slow and risky. A line-by-line diff highlights every added and removed line with line numbers, so you can pinpoint exactly which statements changed and review with confidence before you merge or deploy.

Private by Design

Your source code is never uploaded. Both versions are read and compared entirely in your browser, which makes Diff Shuttle safe for proprietary algorithms, unreleased features, and any code you are not allowed to paste into a remote service.

Works With Any Language

The diff treats code as text, so it works for JavaScript, Python, Go, Rust, Java, C, C++, PHP, Ruby, SQL, shell scripts, and everything in between. One tool covers your whole stack without language-specific setup.

Free With No Limits

There is no sign-up, no paywall, and no cap on comparisons. Ignore Whitespace, Ignore Case, Side by Side and Unified views, and a text export are all included at no cost.

Common Scenarios

Reviewing a Change Before Merge

When someone sends you a revised file outside of version control, you still need to know precisely what they touched. Paste the old and new code into Diff Shuttle, switch to Side by Side, and every added and removed line stands out with line numbers. Reviewers approve faster and never miss a sneaky change that slipped in alongside the intended fix.

Diffing Two Config or Script Files

Two environments behaving differently often comes down to one line in a YAML, TOML, .ini, or shell file. Drop both files into the tool, enable Ignore Whitespace, and the changed line is obvious. Because the comparison is local, you can safely diff production configuration and deploy scripts without exposing them.

Comparing Code From Two Sources

When you copy a snippet from documentation, a forum answer, or an AI assistant and want to know how it differs from your current implementation, a quick paste-and-diff shows the gap instantly. The difference percentage gives a fast read on how far apart the two versions really are.

Resolving a Lost Edit

If you have two copies of a file and are not sure which one contains your latest work, diff them to see which edits exist where. Use Swap to flip the sides if the additions and deletions look reversed, then export the result so you have a record of what you kept.

Tips and Best Practices

Always Try Ignore Whitespace on Reformatted Code

Auto-formatters like Prettier, Black, or gofmt can rewrite indentation across an entire file. Turning on Ignore Whitespace strips that noise so you see only the lines whose actual content changed.

Use Unified View for Patch-Style Review

Unified view stacks additions and deletions in one column with both line numbers, which reads like a Git patch and is compact for long files with scattered edits. Side by Side is better when you want to read two complete versions in parallel.

Load Files by Their Real Extension

Selecting or dropping a file with its native extension (.ts, .py, .go, and so on) keeps your content intact and avoids the unsupported format warning. The tool reads it as text, so the language does not change how the diff works.

Export the Diff Into Your Review

Use Export as Text to capture a patch-style report with plus and minus prefixes and a statistics summary. Paste it into a pull request description, a commit message, or a ticket so teammates can follow the change even without opening the tool.

Diff One File at a Time

The tool compares two text inputs, so review changes file by file rather than pasting an entire repository at once. Smaller, focused comparisons are easier to read and make the statistics far more meaningful.

Compared to Alternatives

The git diff command is the gold standard for tracked code, but it only helps when both versions already live in a repository and you are comfortable in the terminal. For two loose snippets, a file a colleague emailed, or code you pasted from a chat, Diff Shuttle is faster: paste both sides, read the color-coded result, and you are done — no repo, no staging, no command-line flags.

Diffchecker.com is a popular web tool, and it works, but its free tier processes your code on a remote server and pushes you toward a paid plan for larger files and extra features. Diff Shuttle runs the entire comparison locally in your browser, so your source code never leaves your machine, there is no account to create, and every option including the text export is free.

Editors like VS Code can compare two files, but you first have to save both versions to disk and open the editor, which is overkill for a quick check. A browser-based diff keeps the workflow lightweight while still giving you line numbers, side-by-side and unified views, and full privacy.

Frequently Asked Questions

Is the code diff tool free?

Yes. Diff Shuttle is completely free with no registration, no watermarks, and no limit on how many code comparisons you run.

Is my code uploaded to a server?

No. The comparison runs entirely in your browser. Both files are read locally and nothing is ever sent to a server, so proprietary and unreleased source code stays private.

Which languages and file types are supported?

Any plain-text source file works, including .js, .jsx, .ts, .tsx, .py, .java, .c, .cpp, .h, .go, .rs, .php, .rb, .swift, .kt, .sql, .sh, .html, .css, .xml, .yaml, .toml, and more. The diff is language-agnostic and treats your code as text.

Can I ignore indentation and whitespace changes?

Yes. Turn on Ignore Whitespace so reindentation, tab-versus-space changes, and trailing spaces are ignored and you see only the lines where real logic changed.

How large a code file can I compare?

You can upload source files up to 10 MB per side, which covers nearly any single file. Pasted content is limited only by your browser's available memory.

Can I download the comparison?

Yes. Click Export as Text to download a patch-style report with added lines prefixed by a plus sign, removed lines by a minus sign, and a statistics summary you can paste into a pull request or commit message.

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