Hashing, encode, decode: https://emn178.github.io/online-tools/index.html
Online customizable icon, picture https://undraw.co/
Simple REST Request Catcher https://webhook.site/ or https://requestcatcher.com/
Generate mock data .csv file to test: https://www.mockaroo.com/
Convert cURL to C# code: curl to C# converter (olsh.me)