Getting CORS error while uploading files to Amazon S3 using presigned url

My issue was that even after doing the following I got the same CORS error - for some reason - getSignedUrl returned a url like so:

https://my-bucket.s3.us-west-2.amazonaws.com/bucket-folder/file.jpg

I've removed the region part - us-west-2 part - and that fixed it ‍♂️

So instead it is now

https://my-bucket.s3.amazonaws.com/bucket-folder/file.jpg

Some browsers do not support CORS requests from Localhost, such as Chrome. Try using lvh.me:4200 for testing.

While it's true that localhost may not be supported by your browser as a valid origin to match against AllowedOrigin, you might also need to check that the content being fetched from S3 actually correctly has the correct headers that you expect and that your bucket is setup correctly. You can do so via chrome developer tools: https://developers.google.com/web/tools/chrome-devtools/network-performance/reference#headers

http://127.0.0.1 is also a valid domain for localhost (on most OSes) that should be compatible with most browsers for matching against AllowedOrigin.

What you are looking for is cor_rules

s3 = boto3.resource('s3')
bucket_cors = s3.BucketCors(bucket_name='bucket_name', cors_rules=[{
"AllowedOrigins": "*",
}])

I am not sure about if this code will work, maybe you'll need to specify other cors_rules like AllowedHeaders as well. Checkout the documentation:

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/s3.html#id250