Bootstrap 4 has been a massive undertaking that touches nearly every line of code. We’re stoked to share it with you and hear your feedback. We’ve got a lot of news to share with you, so let’s jump right into it.
There are a ton of major changes to Bootstrap and it’s impossible to cover them all in detail here, so here are some of our favorite highlights:
- Moved from Less to Sass. Bootstrap now compiles faster than ever thanks to Libsass, and we join an increasingly large community of Sass developers.
- Improved grid system. We’ve added a new grid tier to better target mobile devices and completely overhauled our semantic mixins.
- Opt-in flexbox support is here. The future is now—switch a boolean variable and recompile your CSS to take advantage of a flexbox-based grid system and components.
- Dropped wells, thumbnails, and panels for cards. Cards are a brand new component to Bootstrap, but they’ll feel super familiar as they do nearly everything wells, thumbnails, and panels did, only better.
- Consolidated all our HTML resets into a new module, Reboot. Reboot steps in where Normalize.css stops, giving you more opinionated resets like
box-sizing: border-box, margin tweaks, and more all in a single Sass file.
- Brand new customization options. Instead of relegating style embellishments like gradients, transitions, shadows, and more to a separate stylesheet like v3, we’ve moved all those options into Sass variables. Want default transitions on everything or to disable rounded corners? Simply update a variable and recompile.
- Dropped IE8 support and moved to rem and em units. Dropping support for IE8 means we can take advantage of the best parts of CSS without being held back with CSS hacks or fallbacks. Pixels have been swapped for rems and ems where appropriate to make responsive typography and component sizing even easier. If you need IE8 support, keep using Bootstrap 3.
- Improved auto-placement of tooltips and popovers thanks to the help of a tool called Tether.
- Improved documentation. We rewrote it all in Markdown and added a few handy plugins to streamline examples and code snippets to make working with our docs way easier. Improved search is also on it’s way.
- And tons more! Custom form controls, margin and padding classes, new utility classes, and more have also been included.
And that barely scratches the surface of the 1,100 commits and 120,000 lines of changes in v4 so far. Plus, we’re not even done yet!