Ask HN: What's the most interesting free API you've discovered?

I've been exploring "no-auth" APIs lately - services you can call directly from the browser without registration, API keys, or credit cards.

It's surprising how many useful ones are out there. A few I've found:

- dog.ceo/dog-api - Random dog images (surprisingly well-maintained) - ipify.org - Get client IP in one line - open-meteo.com - Weather data, no limits - randomuser.me - Fake user data for prototypes

What fascinates me is these seem to just... work. No "free tier" with hidden limits, no forced email signup, no credit card "for verification."

I'm curious what other hidden gems the community has discovered?

Especially interested in: - APIs that have been reliably running for years - Unusual use cases (not just another lorem ipsum generator) - Services where you wonder "how is this still free?"

What have you stumbled upon?