Etag definition changed in Amazon S3


I've used Amazon S3 a little bit for backups for some time. Usually, after I upload a file I check the MD5 sum matches to ensure I've made a good backup. S3 has the "etag" header which used to give this sum.

However, when I uploaded a large file recently the Etag no longer seems to be a md5 sum. It has extra digits and a hyphen "696df35ad1161afbeb6ea667e5dd5dab-2861" . I can't find any documentation about this changing. I've checked using the S3 management console and with Cyberduck.

I can't find any documentation about this change. Any pointers?

Best Solution

If any file is being uploaded with multipart then you will always get such type of ETag. But if you upload whole file as single file then you will get ETag as before.

Bucket Explorer providing you normal ETag till 5Gb upload in multipart operation. But more then it is not providing.


The ETag for an object created using the multipart upload api will contain one or more non-hexadecimal characters and/or will consist of less than 16 or more than 16 hexadecimal digits.