Diff Checker – Free Online Tool
Free online diff checker & code comparison tool. Compare text, code, JSON, XML, and more with syntax highlighting, side-by-side view, and detailed diff statistics. 100% client-side.
The Most Powerful Free Diff Checker Online
Our diff checker is built on the Monaco Editor — the same engine that powers VS Code. Compare any two pieces of text or code with character-level precision, syntax highlighting for 25+ languages, and both side-by-side and inline viewing modes. Get instant diff statistics showing exactly how many lines were added, removed, and modified.
Built on VS Code's Monaco Engine
Unlike basic diff tools that use simple line matching, our tool uses the Monaco Editor's advanced diff algorithm that understands code structure. It provides accurate character-level highlighting, bracket matching, code folding, and intelligent word wrapping — the same diff quality you see in VS Code and GitHub pull requests.
Why Developers Choose Our Diff Checker
No ads, no account required, no file size limits, and 100% private. Your code never leaves your browser. We support 25+ programming languages with full syntax highlighting, offer keyboard shortcuts for navigating between changes, provide detailed diff statistics, and save your comparison history locally. It is the fastest and most feature-rich free diff checker available online.
Who Benefits from This Diff Checker
Software developers comparing code changes and reviewing pull requests. DevOps engineers diffing configuration files. Technical writers comparing document revisions. Database administrators comparing SQL queries. QA engineers verifying test output changes. Students comparing assignment versions. Anyone who needs to find exact differences between two pieces of text quickly and privately.
How to Use Diff Checker
- 1
Paste your original text in the left panel or drag-and-drop a file
- 2
Paste the modified version in the right panel
- 3
Differences are highlighted instantly — green for additions, red for deletions. Use the toolbar to switch between side-by-side and inline views, change the language for syntax highlighting, toggle whitespace comparison, or format JSON before comparing
Frequently Asked Questions
Everything you need to know about the Diff Checker.
Is this diff checker completely free?
Yes, 100% free with no limits. No account required, no daily usage caps, no file size restrictions, and no watermarks. All processing happens in your browser using the Monaco Editor engine, so there are no server costs.
What programming languages are supported?
We support 25+ languages including JavaScript, TypeScript, Python, Java, C, C++, C#, Go, Rust, PHP, Ruby, HTML, CSS, JSON, XML, YAML, SQL, Markdown, Shell/Bash, Dockerfile, and plain text. Each language gets full syntax highlighting in the diff view.
Is my code safe and private?
Absolutely. Your code never leaves your device. The entire comparison runs locally in your browser using the Monaco Editor engine. We have no servers that receive, process, or store your code. This makes it safe for comparing proprietary source code, configuration files with secrets, and sensitive documents.
Can I compare JSON files with formatting differences?
Yes! Use the Format JSON button to auto-format both sides before comparing, which eliminates false differences caused by inconsistent formatting. The tool will then show only the actual content changes, not whitespace or indentation differences.
What keyboard shortcuts are available?
Alt+Down and Alt+Up (or F7/Shift+F7) navigate between changes. The Monaco Editor also supports all standard shortcuts like Ctrl+F for find, Ctrl+G for go-to-line, Ctrl+Z for undo, and Ctrl+Shift+Z for redo. Both panels are fully editable.
Can I upload files instead of pasting text?
Yes! You can drag and drop files directly onto either panel, or use the upload buttons. The tool reads the file contents locally in your browser and loads them into the editor. Supported formats include any text-based file.