Text Diff Checker
Compare two texts side by side and highlight every difference. Character-level detection with merge support.
What Is Text Diff Comparison?
Text diff comparison is an online tool that compares two texts and visually highlights the differences. It's useful for code reviews, document revision checks, configuration file change verification, and any situation where you need to precisely identify text differences.
sakutto.ai's text diff tool processes everything in your browser — the texts you compare are never sent to any server. You can safely compare source code and confidential documents.
Added, deleted, and modified lines are color-coded for instant visibility, with support for both line-level and character-level diff display. Great for programming change reviews, contract revision checks, and translation proofreading. Free, no sign-up required.
How to Use
Enter your text
Paste or type the original text on the left and the modified text on the right.
Review the differences
Differences are highlighted in real time as you type. Added lines appear in green; deleted lines in red.
Merge & navigate
Use the arrow buttons to jump between changes. Use the merge buttons to accept changes from either side.
Features
- Character-level diff highlighting pinpoints exactly what changed
- Switch between side-by-side and unified (inline) views
- One-click merge to accept changes from either side
- Navigation buttons to jump between changes quickly
- Runs entirely in your browser — no data is sent to any server
- Full support for CJK characters and multibyte text
- Responsive design that works smoothly on mobile devices
Why Text Diff Checker on sakutto is safe
Many online tools upload your files to external servers for processing. This tool never sends your text data to any server — everything is processed entirely in your browser.
* Some AI-powered tools require server-side processing. Tools that send data to a server will always notify you beforehand.
| Comparison | Typical online tools | sakutto |
|---|---|---|
| Where data is sent | Uploaded to external servers | Nowhere — processed in your browser |
| Data leak risk | Risk during transfer and server storage | No risk — no network transfer occurs |
| External traffic | File data travels over the internet | No file data appears in network logs |
| Offline use | Not possible (server required) | Works offline after initial load |
How browser-based processing works
- WebAssembly (WASM): Processes text data in your browser at near-native speed. No server communication occurs.
- Web Workers: Runs on a background thread separate from the main thread, so your browser stays responsive during processing.
- After processing, your browser automatically frees the data from memory. No text data remains outside your device.
For IT security teams: How to verify
You can verify that sakutto never sends your text data externally by checking the Network tab in your browser's DevTools while using the tool. You'll see that no requests involving your text data are made. This can also serve as documentation for your IT security team.
Frequently Asked Questions
Is my data safe?
Yes. All processing happens entirely in your browser, and your text is never sent to any server.
Is there a limit on text length?
There is no hard limit, though very long texts (tens of thousands of lines) may increase browser memory usage. For typical use cases, there are no issues.
Can I compare programming code?
Absolutely. This tool works with any kind of text — source code, config files, prose, and more. A monospaced font is used for clear, code-friendly display.
What is the merge feature?
When a difference is detected, you can choose to accept the content from either the left (original) or right (modified) side. This makes it easy to selectively apply changes and build your final text.
Does it work on mobile?
Yes. On mobile devices, the tool automatically switches to unified (inline) view for a comfortable experience.
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