FWIW (and possibly not related to the original issue; posting here in case it helps someone finding this via Google) I was running into similar issues in IE11 in a VM, but then I realised the following option was being passed to the `Map()` constructor: `failIfMajorPerformanceCaveat: true` This will cause MapboxGL to throw the "Failed to initialize WebGL" error if running on a particularly rubbish platform.