Diff Checker

What is Diff Checker

Last reviewed: April 18, 2026

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)

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

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

Common errors

FAQ

Related tools

Continue the workflow with related tools for diff, adjacent input and output steps, or other utilities in the same category. You can also browse the full Visual & Testing Tools category for more options.