Tailwind CSS 4.3.3 is out: highlights and upgrade guide

What's included in Tailwind CSS 4.3.3

Details from the official release page.

Fixed

• Support --watch --poll[=ms] in @tailwindcss/cli when filesystem events are unreliable or unavailable (#20297)
• Canonicalization: match arbitrary hex colors against theme colors case-insensitively (e.g. bg-[#fff] and bg-[#FFF] → bg-white) (#20298)
• Prevent Preflight from overriding Firefox's native iframe:focus-visible outline styles (#20292)
• Ensure theme('colors.foo') in JS plugins resolves correctly when both --color-foo and --color-foo-bar exist (#20299)
• Ensure fractional opacity modifiers work with named shadow sizes like shadow-sm/12.5, text-shadow-sm/12.5, drop-shadow-sm/12.5, and inset-shadow-sm/12.5 (#20302)
• Parse selectors like [data-foo]div as two selectors instead of one (#20303)
• Ensure @tailwindcss/postcss rebuilds when a preprocessor like Sass changes the input CSS without changing the input file on disk (#20310)
• Ensure CSS nesting is handled even when Lightning CSS isn't run, such as in @tailwindcss/browser and Tailwind Play (#20124)
• Prevent achromatic theme colors from shifting hue when mixed in polar color spaces like oklch (#20314)
• Ensure --spacing(0) is optimized to 0px instead of 0 so it remains a ` when used incalc(…)` (#20319)
• Load @parcel/watcher only when needed in @tailwindcss/cli --watch mode, so one-off builds and --watch --poll work when @parcel/watcher can't be loaded (#20325)
• Use explicit platform fonts instead of system-ui and ui-sans-serif so CJK text respects the page's lang attribute on Windows (#20318)
• Prevent @tailwindcss/upgrade from rewriting ignored files when run from a subdirectory (#20329)
• Ensure earlier @source rules pointing to nested files are scanned when later @source rules point to files in parent folders (#20335)
• Prevent @tailwindcss/vite from triggering full page reloads when scanned files are processed by Vite but haven't been loaded as modules yet (#20336)