How to pass 'Content-MD5' to request header in Write-S3Object command (powershell)

You can allow cmdlet to compute this itself, via the -CalculateContentMD5Header <Boolean> option, which will generate the header based on your content, and include this with the request. S3 will validate this header as part of the PutObject operation.

If you want to pass a manually or precomputed value, set the above to false and pass the header as a custom header.

 -HeaderCollection @{ 'Content-MD5' = 'asdfasdfasdfsa'}

Again, S3 will compare this to the uploaded object after receiving the content. If the MD5 does not match the value S3 computes for the received content, the upload will fail.