An incredibly useful resource, well maintained by some of the best people in the PKI space, recently quoted by US-CERT [1] and so quick to use that I try it before starting to use any browser.

A year ago it made me find out that the most popular iOS Tor browser doesn't check certificates at all. [2] (Use OnionBrowser instead.)

[1] https://www.us-cert.gov/ncas/alerts/TA17-075A [2] https://twitter.com/FiloSottile/status/765230315132559360

For an easter egg, try to click on "Defunct"...