Finds Tailwind CSS v3 syntax that v4 removed or silently redefined - @tailwind directives, bg-opacity-*, outline-none, bare border and ring - with the v4 replacement and a line number. Runs entirely in your browser — nothing is uploaded.
Same engine as the VS Code extension, byte for byte.
This page is the working piece. The full pack has everything below.
19 rules that find the Tailwind v3 syntax Tailwind v4 removed or silently redefined, in the file you have open, with the v4 replacement on the same line.
A front-end contractor sweeping the same codebase by hand bills 60-120 an hour.
Buy the full version — $29It reads the Tailwind file you have open and reports every construct that Tailwind v4 removed or silently redefined, with the line number and the v4 replacement. It ships 19 rules. On the bundled 73-line v3 fixture they raise 35 findings; on the migrated copy of the same file they raise 0.
Front-end developers and agency teams moving a Tailwind CSS v3 codebase to v4, and anyone reviewing Tailwind markup an AI wrote. Models trained before January 2025 still emit v3 syntax by default, so a freshly generated component can carry @tailwind directives and bg-opacity-* into a v4 build.
The upgrade tool rewrites the utilities it can rename and stops. It cannot see the silent cases, because they still compile: bare border now takes currentColor instead of gray-200, bare ring is 1px instead of 3px, shadow-sm is one step larger, and outline-none no longer keeps a focus ring.
Free: scan the file you have open and read every finding, all 19 rules, with line numbers and replacements. That finishes the file in front of you. The licence key adds scale and ownership: one command scans every file in the workspace and writes a dated Markdown migration report you can hand to your team.
A front-end contractor sweeping the same codebase by hand bills 60-120 an hour, and the silent cases need a visual diff of every component rather than a search. This extension is 29 dollars once, with one licence key per person or team seat and a 7-day full refund.
One question, answered by the person who built it. Your email only if you want the answer sent.