Keyvalue
Simple key-value storage REST API for quick prototyping
Creates diagrams from textual descriptions.
Kroki API is a free Development API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
Details from kroki.io.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Simple key-value storage REST API for quick prototyping
Live-tested HTTP, SOCKS4, and SOCKS5 proxies with latency, uptime, and geolocation
The Kroki API is provided by Kroki (kroki.io).
Yes. The Kroki API is listed in the Development category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The Kroki API requires no authentication, so you can start making requests without signing up.
Yes. The Kroki API supports CORS, so front-end JavaScript can call it directly.
Yes. The Kroki API is served over HTTPS, so it's safe to use in production.