Who runs the internet
Not a leaderboard. Concentration. That a handful of companies answer, route, front and vouch for most of the web is a systemic-risk fact, and it is only a fact if you say what you measured it against. So every lane below carries its own denominator, because we know the DNS provider for far more domains than we know the certificate issuer, and pretending otherwise would flatter the numbers.
DNS
Who answers for the internet?
One provider covers half of it. The top 3 hold 95.9% of the 24,157 domains we can see this for.
Who handles its mail? (a domain often uses several)
3 providers cover half of it. The top 3 hold 76.4% of the 24,645 domains we can see this for.
CDN
Who sits in front of it?
One provider covers half of it. The top 3 hold 100.0% of the 39,019 domains we can see this for.
Certificate authorities
Who vouches for its identity?
2 providers cover half of it. The top 3 hold 55.7% of the 8,780 domains we can see this for.
Hosting networks
Whose machines is it actually on?
3 providers cover half of it. The top 3 hold 52.0% of the 38,223 domains we can see this for.
A domain counts once per lane. Providers are collapsed to the company, not the label ("Cloudflare (proxied)" and "Cloudflare" are the same company wearing two hats). Domains where a lane could not be observed are excluded from that lane entirely, rather than counted as a zero: not knowing is not the same as nobody. Every figure comes from a signed observation you can re-verify.