This API allows calculating hashes for publicly available content... SHA1mone!
This allows you to show a badge with checksum for online content.
Example
When calculating the hash for the Google favicon (), which is linked at: https://www.google.com/favicon.ico

<img src="http://michaelchecksum.com/SHA1mone/?url=https://www.google.com/favicon.ico"/>

Unless Google changes the favicon, the expected response is:
49263695F6B0CDD72F45CF1B775E660FDC36C606

Badge calculated by the API:

The API will be size-restricted, for an unlimited-cross-platform experience install the command-line tool:

Alternative: commandline
Install Michael checksum on your machine: 
dotnet tool install -g michaelchecksum.console
To calculate a checkum of a local file: 
michaelchecksum mydownloadedfile.zip
To calculate a checkum of a remote: 
michaelchecksum http://download.com/mydownloadedfile.zip