Put together a list of free APIs you can use without signing up or getting an API key. Grouped by category:

Developer Tools:

• httpbin.org (request testing)
• JSONPlaceholder (fake REST API)
• ipapi.co (IP geolocation)

Crypto:

• CoinGecko (prices, market data)
• exchangerate.host (currency conversion)

Security:

• Have I Been Pwned passwords API
• Various SSL/header checkers

Data:

• wttr.in (weather JSON)
• REST Countries (country data)
• Quotable (random quotes)

Full list with curl examples: http://5.78.129.127/free-apis

Every API in the list includes a copy-pasteable curl command. No signup pages, no rate limit walls on first use.

What APIs would you add to this list?