Azure Blob Storage - Status Code 400 - InvalidBlobOrBlock - The specified blob or block content is invalid

So you sliced your File into chunks using Blob.slice method, and sent to your server one by one, passing the index as id.

aand got this error. And interestingly it occurs after 11th chunk just like this. Why?

Because base64 encoding of the numbers doesn't have the same length. If you check the api docs here, you will see it says block ids have to be same.

There of course could be many other reasons, which are documented below:

• Troubleshooting “InvalidBlock” Exception during upload operation