Freelancer vs Tomba email finder

Freelancer's API mirrors the full marketplace — projects, bids, milestones, messages, and user profiles — behind a standard OAuth 2.0 app-registration flow: a live call to `/api/users/0.1/self/` returns 401 `NOT_AUTHENTICATED` rather than any keyless access, and the OPTIONS preflight explicitly whitelists a custom `Freelancer-OAuth-V1` header, reconfirming OAuth as the real mechanism. A GET against the public `/api/projects/0.1/projects/active/` endpoint succeeds with no key at all and echoes `access-control-allow-origin: *` on both the GET and its preflight, resolving the stored 'unknown' CORS value to fully open. Freelancer's own Python SDK and developer portal document no separate paid tier or metering for the API itself — registering an app is free, with the marketplace's usual project fees applying only to actual freelance transactions, not API calls.

Tomba's Email Finder API discovers and verifies professional email addresses from a company domain or a person's name, and doubles as a B2B prospecting and lead-enrichment tool via linked domain-search and phone-finder endpoints. It authenticates with a paired `X-Tomba-Key`/`X-Tomba-Secret` header set rather than a single token, and a live Origin-header probe confirms it explicitly supports browser CORS, echoing the request Origin with credentials enabled on both a GET and an OPTIONS preflight.