
Security and developer utility API -- malware, vulnerability, and domain checks, no signup.
Presend API is a free Security API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
Free REST API, no key or signup: supply-chain checks (typosquatting, npm maintainer changes, OSV vulnerabilities), security headers, DNS and RDAP lookups, email and IBAN validation.
Details from presend.pages.dev.

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.
Generate merchant-specific and one-time use credit card numbers that link back to your bank
The Presend API is provided by Presend API for Developers (presend.pages.dev). Free REST API, no key or signup: supply-chain checks (typosquatting, npm maintainer changes, OSV vulnerabilities), security headers, DNS and RDAP lookups, email and IBAN validation.
Yes. The Presend API is listed in the Security 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 Presend API requires no authentication, so you can start making requests without signing up.
Yes. The Presend API supports CORS, so front-end JavaScript can call it directly.
Yes. The Presend API is served over HTTPS, so it's safe to use in production.