Diff Checker: Compare Text and Code Online
Paste or drop two versions and see every added, removed and changed line instantly. Works offline, nothing leaves your device.
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TL;DR: paste the original on the left and the changed version on the right — differences appear as you type. Switch between side-by-side and unified views, highlight changes down to single words or characters, ignore whitespace or case, compare JSON with sorted keys and export the result as a .diff patch. All processing happens in your browser.
We built this tool for our own code reviews and content checks at YuSMP Group. If you need more than a comparison — a team to build, refactor or maintain the product behind the code — see our web development services and custom software development.
How do I compare two texts or files?
- Add the original. Paste text into the left field, click to upload a file, or drag and drop it onto the field.
- Add the changed version in the right field the same way.
- Read the result. Removed lines are marked red, added lines green; inside a changed line the exact words or characters are highlighted. Code is shown with syntax highlighting, so changes are easier to read.
- Jump between changes with Alt+↓ and Alt+↑ — handy in long files.
- Export: download a unified
.diffpatch, copy the result, or print it / save as PDF.
Side by side or unified: which view should I use?
| View | Best for | Looks like |
|---|---|---|
| Side by side (split) | Reading edits in prose, contracts, configs; wide screens | Two columns, matching lines aligned |
| Unified | Code review, narrow screens, sharing a patch | One column with - and + lines, like git diff |
Word-level highlighting is the right default for text and code. Switch to character level when you hunt for a typo, a changed digit in a version number or a swapped quote mark.
How do I compare JSON without false differences?
Two JSON files can be identical in data and still look completely different: keys in another order, other indentation, everything on one line. JSON mode first parses both sides, formats them the same way and sorts the keys, and only then compares. You see real changes in values and structure, not formatting noise. If one side is not valid JSON, the tool tells you the line where parsing failed, so you can fix the input first.
What do the ignore options do?
- Ignore whitespace — extra spaces and tabs do not count as changes. Useful after reformatting or a linter run.
- Ignore case —
SELECTandselectare treated as equal. - Ignore blank lines — added or removed empty lines are skipped.
- Ignore line endings (CRLF/LF) — a file saved on Windows and the same file from Linux or macOS stop showing every line as changed.
Common mistakes when comparing files
- Every line is marked as changed. Almost always line endings or indentation: turn on the CRLF/LF or whitespace option.
- Swapped sides. The left field is the original. If you paste the new version on the left, additions appear as deletions.
- Comparing minified files. A file on a single line becomes one huge changed line. For JSON use JSON mode; for code, format both sides first.
- Diffing generated files. Lock files and build output change a lot for small reasons. Compare the source files instead.
Is my data safe?
Yes. The comparison runs entirely in your browser: texts and files are not sent to our server or anyone else's. After the page loads, the tool keeps working even with the network turned off — that is the simplest way to check it yourself. That is why it is safe to compare configs, contracts and code you cannot share.
Limits
Each side accepts up to 5 MB of text — tens of thousands of lines — and the calculation runs in the background, so the page does not freeze. Binary files such as images, archives or Word documents cannot be compared as text: export them to plain text first.
FAQ
Is this diff checker free?
Yes. It is free, with no sign-up and no limit on the number of comparisons. Each side accepts up to 5 MB of text.
Are my texts or files uploaded anywhere?
No. The comparison runs in your browser, and the text never leaves your device. After the page loads, you can switch off the internet and the tool keeps working.
How is this different from git diff?
The result is the same unified diff format, and you can download it as a .diff patch. The difference is that you do not need a repository or a terminal: you paste two versions and see highlights by word or character, and you can switch to a side-by-side view.
Can I compare two JSON files?
Yes. JSON mode formats both sides and sorts the keys before comparing, so you only see real changes in data and structure. If the JSON is invalid, the tool shows the line with the error.
Why is every line shown as changed?
Usually the files use different line endings (Windows CRLF vs Unix LF) or different indentation. Turn on the line-ending or whitespace option and the false differences disappear.
Can I compare Word or PDF documents?
Not directly: the tool compares plain text. Copy the text out of the document, or convert it first — for example with our PDF to Word converter — and paste the result.