Diff Checker

Paste two versions of something into the two boxes and see what changed between them, line by line. Added lines are green, removed lines are red, and changed lines are highlighted in yellow, with a running tally of how many lines were added, removed, modified, or left alone. View it inline (one combined column) or side by side, whichever makes the change easier to read.

It's the quick answer to "what's different between these two?" — an old config versus a new one, a colleague's edit versus yours, two versions of a query or a snippet you pasted from different places. Rather than squinting to spot the one line that moved, you get the changes marked clearly.

Toggles for ignore-case and ignore-whitespace let you filter out the noise you don't care about, so a difference in capitalization or indentation doesn't flag a line as changed when the meaning is identical. Everything runs in your browser — nothing you paste is uploaded.

The comparison works at the line level. Both inputs are split on newlines and walked in parallel: matching lines are marked unchanged, a line present only on the right is an addition, a line present only on the left is a removal, and a line that differs in the same position is a modification. It uses a greedy longest-common-subsequence style pass with lookahead to line changes up, which is fast and handles the common cases well — inserted blocks, deleted blocks, and edits in place.

The ignore-case option lowercases both sides before comparing; ignore-whitespace collapses runs of whitespace and trims each side, so reformatting or indentation changes don't register as differences. The stats bar counts each category. Because the diff is line-based, a change is reported for the whole line — it highlights that a line differs but doesn't pinpoint the specific characters within it (in modify rows it shows the before and after so you can compare directly).

This is a lightweight in-browser diff, not the optimal-minimal-edit algorithm a version control system uses, so on heavily rearranged text the grouping can differ from what git shows. All processing is client-side.

Git's diff and dedicated merge tools (Beyond Compare, Meld) offer word-level highlighting, three-way merges, and syntax awareness. This tool is for the fast, no-setup case: you have two blobs of text and want to see the differences right now, without committing anything or opening an app. Paste, compare, done.

For diffing tracked files in a repository, git diff is the right tool. For comparing arbitrary text you've pasted — two config versions, two drafts, output from two runs — this is quicker, and the ignore-case and ignore-whitespace toggles handle the common "same content, different formatting" situation cleanly.