Diff Checker
Compare two texts side by side and see exactly what changed.
Compare two texts side by side and see exactly what changed.
This free diff checker lets you compare two blocks of text and see exactly what was added, removed, or left unchanged. Differences are displayed in a clean, color-coded format: green for added lines and red for removed lines. The tool runs entirely in your browser with no data sent to any server, making it safe for comparing sensitive documents, code, and configuration files.
The tool uses a line-by-line comparison algorithm based on the longest common subsequence (LCS) technique. It identifies which lines are shared between the original and modified texts, then marks the remaining lines as additions or deletions. This approach produces clean, readable diffs similar to what you see in version control systems like Git.
Paste your original text in the left textarea and the modified version in the right textarea. Click "Compare" to generate the diff output. Added lines appear in green with a plus sign, removed lines appear in red with a minus sign, and unchanged lines are shown in their normal color. Line numbers are displayed on both sides for easy reference.
After running a comparison, the tool displays summary statistics showing the number of lines added, removed, and unchanged. This gives you a quick overview of how much has changed between the two versions without needing to read through the entire diff output.
All comparison logic runs locally in your browser using JavaScript. Your text is never uploaded to any server, making this tool suitable for comparing proprietary code, confidential documents, credentials, and other sensitive information.