Amazon S3 Permission problem - How to set permissions for all files at once?

I used Cloudberry Explorer to do the job :)

You can select which directory you want it to be public.

Press on "more" and mark it as public; it will make the directory and all the files to be accessible as public.

You can only modify ACLs for a unique item (bucket or item), soy you will have to change them one by one.

Some S3 management applications allows you to apply the same ACL to all items in a bucket, but internally, it applies the ACL to each one by one.

If you upload your files programmatically, it's important to specify the ACL as you upload the file, so you don't have to modify it later. The problem of using an S3 management application (like Cloudberry, Transmit, ...) is that most of them uses the default ACL (private read only) when you upload each file.

I suggest that you apply a bucket policy¹ to the bucket where you want to store public content. This way you don't have to set ACL for every object. Here is an example of a policy that will make all the files in the bucket mybucket public.

{
    "Version": "2008-10-17",
    "Id": "http better policy",
    "Statement": [
        {
            "Sid": "readonly policy",
            "Effect": "Allow",
            "Principal": "*",
            "Action": "s3:GetObject",
            "Resource": "arn:aws:s3:::mybucket/sub/dirs/are/supported/*"
        }
    ]
}

That * in "Resource": "arn:aws:s3:::mybucket/sub/dirs/are/supported/*" allows recursion.

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¹ Note that a Bucket Policy is different than an IAM Policy. (For one you will get an error if you try to include Principal in an IAM Policy.) The Bucket Policy can be edit by going the root of the bucket in your AWS web console and expanding Properties > Permissions. Subdirectories of a bucket also have Properties > Permissions, but there is no option to Edit bucket policy