As of the most recent release, Looker supports:
Level 1 browsers
Level 1 browsers are fully supported for use with Looker. For Level 1 browsers, Looker supports the current and previous major releases of the browser. Each time a new browser version is released, Looker supports the newest version and stops supporting the third most recent version.
Level 2 browsers
Internet Explorer 11 is not supported. For more information, see our Best Practices page, Looker Internet Explorer 11 support.