I see that speedtest.net is using lets encrypt for all of “its” servers. But one thing bothers me. Rate limits, acording to your rate limits https://letsencrypt.org/docs/rate-limits/ there is limit 50 new certificates per week per domain. But speedtest.net has aprox 8000 servers, each one with unique https certificate
If you are a large hosting provider or organization working on a Let’s Encrypt integration, we have a rate limiting form that can be used to request a higher rate limit. It takes a few weeks to process requests, so this form is not suitable if you just need to reset a rate limit faster than it resets on its own.