Corporate carbon emissions disclosures (scope 1, 2 and 3), company-reported and estimated.
Mycelium API is a free Environment API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.

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Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Open data from Great Britain’s Electricity System Operator
Yes. The Mycelium API is listed in the Environment 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.
Yes. The Mycelium API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the Mycelium API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Mycelium API is served over HTTPS, so it's safe to use in production.