W015

Detected what appears to be Bootstrap v4 or later. This version of Bootlint only supports Bootstrap v3.

Based on the version of Bootstrap's jQuery plugins or based on the apparent version number in the URL of a Bootstrap-related <script> or <link rel="stylesheet"> tag, it appears that you are using version 4 of Bootstrap. The version of Bootlint you are using only supports Bootstrap version 3. You may need to update your copy of Bootlint to a newer version.

This check is heuristic and thus can have false positives or negatives depending on what URLs you're using for Bootstrap or for Bootstrap-related third-party libraries.

Bootlint documentation wiki content is licensed under the CC BY 3.0 License, and based on Bootstrap's docs which are copyright Twitter, Inc.