Prompt Diff

Prompt Diff compares two pieces of text line by line using a Longest Common Subsequence (LCS) algorithm and renders a unified diff view with additions highlighted green, removals highlighted red, and unchanged lines left plain. Each version is entered into its own Version A and Version B textarea, and the comparison produces counts of added, removed, and unchanged lines that you can copy as a prefixed diff.

1. Paste the original text into the Version A card. 2. Paste the revised text into the Version B card. 3. Click the Compare button to compute the diff. Editing either textarea automatically hides the previous result so a fresh comparison is required. 4. After the result appears, read the added (+) / removed (-) / unchanged (=) counters in the header and click Copy to copy the diff text prefixed with +, -, or a space for each line.

Each result line begins with a prefix symbol: + marks a line present only in Version B (added), - marks a line present only in Version A (removed), and a blank prefix marks a line common to both versions. The header shows three counters: a green +N for added lines, a red -N for removed lines, and a muted =N for unchanged matching lines. When both inputs are identical, the view shows only unchanged lines and the add/remove counters are zero.