Diff Checker
Used 4,300 times
Paste your original text on the left and the modified version on the right. Hit Compare to see every addition, deletion, and unchanged line with full stats.
What is a Diff Checker?
A diff checker compares two text blocks and highlights exactly what changed between them. This tool uses a Longest Common Subsequence (LCS) algorithm — the same approach used by git diff — to identify added lines (green), removed lines (red), and unchanged lines (gray), along with left/right line numbers and a summary of changes.
How to Use
- Paste the original text into the Original (left) box.
- Paste the modified text into the Modified (right) box.
- Click Compare — every line is classified as added, removed, or unchanged.
- Use Swap to reverse the comparison, or Clear to reset both panes.
Common Use Cases
- Config file changes — Compare two versions of a YAML, JSON, or TOML config before deploying.
- Code review — Quickly spot what changed in a snippet without opening a full git client.
- Log comparison — Diff two log segments to isolate behavior changes between runs.
- Documentation edits — Track what was reworded or removed in a draft.
FAQs
Is the diff line-based or character-based?
Line-based. Each line is treated as a unit — a line that changed even by one character is shown as removed and re-added. This matches the behavior of git diff.
Does whitespace matter?
Yes — trailing spaces or different line endings (CRLF vs LF) will register as changes. Normalize line endings before comparing if you want to ignore them.
How large can the inputs be?
The LCS algorithm's memory use scales with m × n (lines in each input). For very large files, the comparison may be slow. For files over a few thousand lines, prefer git diff or diff in a terminal.