Compare Text & Code Instantly
Free diff checker with syntax highlighting, character-level diffs, and dark mode. No account. No limits. No data sent to servers.
Paste text in both panels above to compare
Or to see how it works
What is a diff checker?
A diff checker compares two versions of text or code and highlights what changed — additions in green, deletions in red. It's an essential tool for developers reviewing code changes, writers comparing document revisions, and anyone tracking what's different between two files.
Syntax highlighting for 15+ languages
DiffCheck supports JavaScript, TypeScript, Python, JSON, HTML/XML, YAML, SQL, CSS, Go, Rust, Java, C/C++, Bash, and Markdown. Select your language from the dropdown to get color-coded syntax on top of the diff highlighting, making code reviews significantly easier to read.
Free alternative to Diffchecker
As Diffchecker moves core features behind paid plans, DiffCheck offers the same side-by-side and inline diff views, character-level highlighting, and syntax support — completely free, with no account required and no data sent to any server.
Character-level diff highlighting
Beyond line-level diffs, DiffCheck highlights the exact words and characters that changed within each line. This fine-grained view is especially useful for spotting small typos, variable renames, or single-character differences that line-level diffs would hide.
Privacy-first, client-side only
All diffing happens in your browser using JavaScript. Your text is never uploaded to any server. This makes DiffCheck safe to use with sensitive data — source code, contracts, configuration files, or any private document you need to compare.
Side-by-side and inline views
Toggle between side-by-side view (original and modified shown in parallel columns) and inline/unified view (changes interleaved in a single column with + and − prefixes). Side-by-side is the default on desktop; inline is the default on mobile for readability.
How to compare text online
- 1
Paste your original text
Put the original version in the left editor (labeled "Original"). This is the baseline you're comparing from.
- 2
Paste your modified text
Put the updated version in the right editor (labeled "Modified"). This is what you're comparing to.
- 3
Read the diff
Lines in green were added. Lines in red were removed. Within each changed line, the exact words and characters that changed are highlighted more intensely.
- 4
Pick a view and language
Switch between side-by-side and inline views with the toggle. If you're diffing code, select a language from the dropdown for syntax highlighting on top of the diff.
Frequently asked questions
Is DiffCheck really free?
Yes, completely. All features are free with no rate limits and no signup. The tool is ad-supported to cover hosting costs, but there are no paid tiers or paywalls.
Is my text safe to paste here?
Yes. All diff computation runs in your browser using JavaScript. Your text is never sent to any server, never stored, and never logged. You can safely paste source code, credentials, contracts, or any private content.
What's the difference between side-by-side and inline view?
Side-by-side shows the original and modified text in two parallel columns — great for desktop where you can see both at once. Inline (also called unified) view interleaves additions and deletions in a single column, which works better on narrow screens and is closer to what `git diff` shows in a terminal.
Does DiffCheck work for code?
Yes. Select a language from the dropdown and the diff output gets full syntax highlighting on top of the diff colors. This makes it much easier to review code changes compared to a plain text diff.
How is this different from Diffchecker?
Diffchecker was the go-to free diff tool for years, but has moved core features behind paid plans. DiffCheck gives you the same functionality — side-by-side view, inline view, character-level highlighting, syntax highlighting — permanently free, with no account required.
Can I use DiffCheck offline?
Once the page loads, the diff tool itself works without an internet connection. All the diffing logic is JavaScript running locally in your browser.