Diff Checker
Compare two blocks of text side by side and highlight every added, removed and unchanged line.
About the Diff Checker
The DevGizmo Diff Checker computes a line-level diff between two blocks of text and presents the result in a colour-coded side-by-side view. Lines that exist only in the original are highlighted in red; lines that appear only in the modified version are highlighted in green; lines common to both remain unstyled.
The diff is computed using the Longest Common Subsequence (LCS) algorithm — the same underlying algorithm used by version control systems such as Git. The comparison runs entirely in your browser with no data ever sent to a server.
How to Use
- Paste your original text into the left panel.
- Paste the modified version into the right panel.
- The diff output updates automatically below, with a summary of added and removed lines.
- Blank alignment rows are inserted to keep corresponding equal lines vertically aligned across both panels.
Common Use Cases
Developers use diff checkers to review configuration file changes, compare API responses, or spot regressions in generated output. Technical writers use them to review document revisions. QA engineers use them to compare expected versus actual test output. The tool is particularly useful for comparing JSON, YAML, CSV and plain-text log files.