UK Government coronavirus data, including deaths and cases by region.
Coronavirus in the UK API is a free Health API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
Showing public health data across England
Details from coronavirus.data.gov.uk.

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Maps, datasets, applications and more in the context of COVID-19
The Coronavirus in the UK API is provided by UKHSA data dashboard (coronavirus.data.gov.uk). Showing public health data across England
Yes. The Coronavirus in the UK API is listed in the Health 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 Coronavirus in the UK API requires no authentication, so you can start making requests without signing up.
CORS support for the Coronavirus in the UK API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Coronavirus in the UK API is served over HTTPS, so it's safe to use in production.