Tailwind CSS v3.1.0 — Release Notes & Engineering Impact

We just released Tailwind CSS v3.1 — the first new feature release since v3.0 came out last year! [Read the announcement post](https://tailwindcss.com/blog/tailwindcss-v3-1) for all the details, and [watch the YouTube video](https://www.youtube.com/watch?v=nOQyWbPO2Ds) for a tour of some of the highlights. --- ### Added - Support PostCSS `Document` nodes ([#7291](https://github.com/tailwindlabs/tailwindcss/pull/7291)) - Add `text-start` and `text-end` utilities ([#6656](https://github.com/tailwindlabs/tailwindcss/pull/6656)) - Support customizing class name when using `darkMode: 'class'` ([#5800](https://github.com/tailwindlabs/tailwindcss/pull/5800)) - Add `--poll` option to the CLI ([#7725](https://github.com/tailwindlabs/tailwindcss/pull/7725)) - Add new `border-spacing` utilities ([#7102](https://github.com/tailwindlabs/tailwindcss/pull/7102)) - Add `enabled` variant ([#7905](https://github.com/tailwindlabs/tailwindcss/pull/7905)) - Add TypeScript types for the `tailwind.config.js` file ([#7891](https://github.com/tailwindlabs/tailwindcss/pull/7891)) - Add `backdrop` variant ([#7924](https://github.com/tailwindlabs/tailwindcss/pull/7924), [#8526](https://github.com/tailwindlabs/tailwindcss/pull/8526)) - Add `grid-flow-dense` utility ([#8193](https://github.com/tailwindlabs/tailwindcss/pull/8193)) - Add `mix-blend-plus-lighter` utility ([#8288](https://github.com/tailwindlabs/tailwindcss/pull/8288)) - Add arbitrary variants ([#8299](https://github.com/tailwindlabs/tailwindcss/pull/8299)) - Add experimental `matchVariant` API ([#8310](https://github.com/tailwindlabs/tailwindcss/pull/8310), [34fd0fb8](https://github.com/tailwindlabs/tailwindcss/commit/34fd0fb82aa574cddc5c7aa3ad7d1af5e3735e5d)) - Add `prefers-contrast` media query variants ([#8410](https://github.com/tailwindlabs/tailwindcss/pull/8410)) - Add opacity support when referencing colors with `theme` function ([#8416](https://github.com/tailwindlabs/tailwindcss/pull/8416)) - Add `postcss-import` support to the CLI ([#8437](https://github.com/tailwindlabs/tailwindcss/pull/8437)) - Add `optional` variant ([#8486](https://github.com/tailwindlabs/tailwindcss/pull/8486)) - Add `<alpha-value>` placeholder support for custom colors ([#8501](https://github.com/tailwindlabs/tailwindcss/pull/8501)) ### Fixed - Types: allow for arbitrary theme values (for 3rd party plugins) ([#7926](https://github.com/tailwindlabs/tailwindcss/pull/7926)) - Don’t split vars with numbers in them inside arbitrary values ([#8091](https://github.com/tailwindlabs/tailwindcss/pull/8091)) - Require matching prefix when detecting negatives ([#8121](https://github.com/tailwindlabs/tailwindcss/pull/8121)) - Handle duplicate At Rules without children ([#8122](https://github.com/tailwindlabs/tailwindcss/pull/8122)) - Allow arbitrary values with commas in `@apply` ([#8125](https://github.com/tailwindlabs/tailwindcss/pull/8125)) - Fix intellisense for plugins with multiple `@apply` rules ([#8213](https://github.com/tailwindlabs/tailwindcss/pull/8213)) - Improve type detection for arbitrary color values ([#8201](https://github.com/tailwindlabs/tailwindcss/pull/8201)) - Support PostCSS config options in config file in CLI ([#8226](https://github.com/tailwindlabs/tailwindcss/pull/8226)) - Remove default `[hidden]` style in preflight ([#8248](https://github.com/tailwindlabs/tailwindcss/pull/8248)) - Only check selectors containing base apply candidates for circular dependencies ([#8222](https://github.com/tailwindlabs/tailwindcss/pull/8222)) - Rewrite default class extractor ([#8204](https://github.com/tailwindlabs/tailwindcss/pull/8204)) - Move `important` selector to the front when `@apply`-ing selector-modifying variants in custom utilities ([#8313](https://github.com/tailwindlabs/tailwindcss/pull/8313)) - Error when registering an invalid custom variant ([#8345](https://github.com/tailwindlabs/tailwindcss/pull/8345)) - Create tailwind.config.cjs file in ESM package when running init ([#8363](https://github.com/tailwindlabs/tailwindcss/pull/8363)) - Fix `matchVariants` that use at-rules and placeholders ([#8392](https://github.com/tailwindlabs/tailwindcss/pull/8392)) - Improve types of the `tailwindcss/plugin` ([#8400](https://github.com/tailwindlabs/tailwindcss/pull/8400)) - Allow returning parallel variants from `addVariant` or `matchVariant` callback functions ([#8455](https://github.com/tailwindlabs/tailwindcss/pull/8455)) - Try using local `postcss` installation first in the CLI ([#8270](https://github.com/tailwindlabs/tailwindcss/pull/8270)) - Allow default ring color to be a function ([#7587](https://github.com/tailwindlabs/tailwindcss/pull/7587)) - Don't inherit `to` value from parent gradients ([#8489](https://github.com/tailwindlabs/tailwindcss/pull/8489)) - Remove process dependency from log functions ([#8530](https://github.com/tailwindlabs/tailwindcss/pull/8530)) - Ensure we can use `@import 'tailwindcss/...'` without node_modules ([#8537](https://github.com/tailwindlabs/tailwindcss/pull/8537)) ### Changed - Only apply hover styles when supported (future) ([#8394](https://github.com/tailwindlabs/tailwindcss/pull/8394)) - Respect default ring color opacity (future) ([#8448](https://github.com/tailwindlabs/tailwindcss/pull/8448), [3f4005e](https://github.com/tailwindlabs/tailwindcss/commit/3f4005e833445f7549219eb5ae89728cbb3a2630))