It is not in the same league as Flent, but I really like https://speed.cloudflare.com as an in-browser internet speed test. It's backed by a very densely deployed CDN, it tests both loaded and unloaded latency, and it reports jitter and draws candlestick plots.
Love this for super quick no brainer data. I used to use speedtest.net, by Ookla, back in the day, but this is so much better in so many ways and provides so much more data.
What it has that virtually every speedtest lacks is a packet loss test that floods 1000 packets and checks if it receives a reply. The bad news is sometimes it doesn't work, and sometimes the results are incorrect (indicating packet loss when generally there is no loss which might be more of an indicator that something is wrong with CF).
