[e1g]

FYI, you can add browser support by using noble-hashes[1] for SHA256/HMAC - it's a well-done library, and gives you performance that is indistinguishable from native crypto on any scale relevant to S3 operations. We use it for our in-house S3 client.

[1] https://github.com/paulmillr/noble-hashes

[continuational]

SHA256 and HMAC are widely available in the browser APIs: https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypt...

[e1g]

SublteCrypto is async, and the author specifically said they want their API to be sync.