Summary:
Jake Archibald explains CORS from first principles—origins vs sites, why credentials complicate cross-origin requests, and how the CORS header model evolved. He shows when CORS applies, how to use Access-Control-Allow-Origin, credentials with Access-Control-Allow-Credentials, the importance of Vary for caches/CDNs, and how preflights work for unusual methods/headers. Includes a hands-on playground and gotchas (e.g., method casing in Chrome, header exposure, caching pitfalls).
Excerpt:
"A practical, opinionated deep dive on CORS—why it exists, how it works, and how to configure headers (including credentials, caching, and preflights) without shooting yourself in the foot."
#Web#Security#CORS#HTTP#Browsers
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