There's a migration guide[0]. Having done it this year, it's not too painful, depending on how much you've customized Bootstrap 3 to meet your needs. We've been

There's a migration guide[0]. Having done it this year, it's not too painful, depending on how much you've customized Bootstrap 3 to meet your needs. We've been migrating on a page by page basis, and so usually we wait to migrate a page until our designers come up with an update to the page. [0]http://getbootstrap.com/docs/4.1/migration/ http://getbootstrap.com/docs/4.1/migration/