📖 What is Text Diff Checker?
A diff checker compares two pieces of text and highlights exactly what changed — additions, deletions and modifications — line by line. Developers use it to review code changes, compare config files, check copy edits, verify API response differences and spot unintended modifications before committing.
This tool runs entirely in your browser. Paste your original text on the left and the modified version on the right, and differences are highlighted instantly. Your text is never uploaded to any server.
💡 Example
Input
Original: "The API returns a 200 status code"
Modified: "The API returns a 201 status code with a Location header"
Output
Line 1: changed "200" → "201", added "with a Location header" — deletions in red, additions in green
🛠️ Common Use Cases
- Reviewing code changes before committing to Git
- Comparing configuration files across environments (dev vs production)
- Checking what changed between two versions of a document or contract
- Verifying API response differences between endpoints or versions
- Spotting unintended whitespace, encoding or line-ending changes
📝 How Diff Algorithms Work
Most diff tools use a variant of the Longest Common Subsequence (LCS) algorithm. It finds the longest sequence of lines that appear in both texts in order, then marks everything else as added or removed. The result is the minimum set of changes needed to transform text A into text B.
This is the same algorithm behind git diff, diff on Linux, and code review tools like GitHub Pull Requests.
⚠️ Common Mistakes
- Trailing whitespace differences — invisible spaces at line ends show as changes. Trim both texts first if whitespace is not significant.
- Line ending mismatches — Windows (CRLF) vs Unix (LF) line endings create false diffs on every line. Normalize line endings before comparing.
- Comparing minified code — minified files show as one giant changed line. Beautify both files first, then diff.
- Encoding differences — UTF-8 vs Latin-1 can cause invisible character mismatches
❓ Frequently Asked Questions
Can I compare code files? ▾
Yes — paste any text including code, JSON, YAML, XML, SQL or plain text. The diff highlights changes regardless of format. For best results with code, make sure both versions use the same indentation style.
Does it detect moved lines? ▾
This tool performs a standard line-by-line diff. A line that moves to a different position shows as deleted from the original location and added at the new location. Dedicated code review tools can sometimes detect moves, but a line-level diff is the most reliable comparison.
How do I ignore whitespace differences? ▾
Trim trailing whitespace from both texts before pasting, or normalize indentation. If you are comparing code, use a code formatter on both versions first to eliminate formatting noise.
Is my data private? ▾
Yes — all processing runs entirely in your browser using JavaScript. Your data is never sent to any server.
Is this tool free? ▾
Completely free — no login, no usage limits, and it works offline once the page is loaded.
Yes — completely free, no login required, no usage limits.
Is my data private? ▾
Yes — all processing runs in your browser. Your data is never sent to any server.
Does it work offline? ▾
Yes — once the page is loaded, the tool works without an internet connection.