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Diff Checker

Compare two texts and highlight differences

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What is Diff Checker

Written by Giorgos Kostas. Last reviewed:

Diff Checker compares two blocks of text and shows a side-by-side or inline diff with line-level and character-level change highlighting. Under the hood it uses the Myers diff algorithm — the same one git uses — so the output lines up with what you'd see in a git diff.

Modes include plain text, programming-language-aware (syntax-highlighted diffs), JSON-aware (structural diff across key order changes), and XML-aware.

Why use it

  • Quickly spot the differences between two versions of a config, log, or code snippet without firing up a full IDE.
  • Compare an API response against an expected snapshot during manual testing.
  • Review changes a teammate proposed in a chat or ticket before pulling them into your branch.

Features

  • Myers diff algorithm with line-level changes and character-level refinement inside each changed line
  • Side-by-side and inline (unified) view modes — toggle between them in one click
  • Syntax highlighting for 40+ languages when you pick a language-aware mode
  • JSON-aware mode that treats `{a:1, b:2}` and `{b:2, a:1}` as equivalent (key-order-independent diff)
  • Exports the diff as a patch file (unified diff format) ready to apply with `git apply` or `patch -p1`

How to use Diff Checker

  1. Paste the original. Drop the old version into the left pane. Large inputs (up to a few MB) are supported with virtualized scrolling.
  2. Paste the new version. Drop the new version into the right pane. The diff computes on every edit with debouncing to stay responsive.
  3. Pick a diff mode. Plain text is the default. Switch to language-aware for syntax highlighting, or JSON/XML-aware for structural comparison.
  4. Review changes. Line-level differences are shown with red/green backgrounds; character-level changes inside each line are underlined. A summary footer counts additions and deletions.
  5. Export the patch (optional). Click 'Export patch' to download a unified diff file that you can apply to the original with `patch` or `git apply`.

Example (before/after)

Diff input

Start with the diff input you want to process in Diff Checker.

Diff output

Get a diff result from Diff Checker that is ready to review, copy, and reuse in the next step of your workflow.

Common errors

Unsupported input

The tool may reject input that does not match the expected content, structure, or file type.

Fix: Confirm the tool input requirements and paste the correct type of data.

Incomplete values

Missing fields or partial content can block processing or produce weak results.

Fix: Provide the full required input before running the tool.

Copying placeholder content

Sample or placeholder values can lead to output that looks valid but is not ready for real use.

Fix: Replace placeholders with your actual values before relying on the result.

FAQ

What diff algorithm does this tool use?

Myers diff, the same algorithm used by git, so the output matches what you'd see in `git diff`. For very large inputs with many changes, the tool falls back to Patience diff, which is better at aligning moved blocks of code.

Does Diff Checker ignore whitespace or line endings?

Toggles in the sidebar let you ignore trailing whitespace, collapse consecutive whitespace into one space, and normalize line endings (CRLF vs LF vs CR). Off by default so the diff is exact; enable whichever rules match how your VCS is configured.

How is a JSON diff different from a plain-text diff?

JSON diff parses both inputs, walks the object tree, and reports changes at the property level — so reordering keys, rewriting whitespace, or changing indentation doesn't show as a difference. Plain-text diff would flag all of those.

Can I diff very large files?

Yes, up to about 5 MB per side. Beyond that, the browser's memory footprint gets expensive — the tool switches to a 'summary mode' that only shows changed hunks rather than the full document to stay responsive.

Does the tool handle binary files?

No. Diff Checker is text-only. For binary diffs (images, archives), use a hex-diff tool or a specialized comparison utility — the output of a textual diff on binary data is unreadable anyway.

Can I share a diff result with a teammate?

Yes. The 'Share' button generates a URL that encodes both sides of the diff (compressed) so opening the URL restores the exact comparison. The diff is computed client-side; nothing is stored on the server.

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