I upgraded my site today to use the new Bootstrap framework, compiling from Sass all the way up.

Here were some quirks I discovered because (surprise, surprise) I didn’t read the migration docs:

• The data-toggle attribute has been replaced  with data-bs-toggle so as to identify Bootstrap-specific functionality. The same goes for data-bs-target and data-bs-dismiss. Just grep your entire codebase and be done with it.
• The ml-auto and mr-auto classes have been replaced with ms-auto and me-auto in keeping with changes that incorporate RTL Support . But wait, there’s more…
• All alignment utility classes that previously incorporated left and right have also been replaced with start and end as well. Again, happy grepping!

The one change I personally disagree with is the renaming of the font utilities in favor of what they term brevity and consistency . I think this actually reduces the well-loved readability of Bootstrap syntax and makes it seem more like the garbled atomic mess that is Tailwind CSS.

If do you use Bootstrap and you plan on upgrading, make sure you check out the Bootstrap v5 Migration Docs .