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Asked: 2026-05-23T15:36:17+00:00

I’ve used Amazon S3 a little bit for backups for some time. Usually, after

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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?

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  1. Editorial Team

    You will always get this style of ETag when uploading an multipart file. If you upload the whole file as a single file, then you will get an ETag without the -{xxxx} suffix.

    Bucket Explorer will show the unsuffixed ETag for a multipart file up to 5Gb.

    AWS:

    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.

    Reference: https://forums.aws.amazon.com/thread.jspa?messageID=203510#203510

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