As part of the web check request, you can post data in the request body for HTTP checks and as a data string for TCP checks. You can enter the content in the "Request data" section when adding or editing a check.
For HTTP check types:
Each key-value pair is separated by an '&' character, and each key is separated from its value by an '=' character. Keys and values are both escaped by replacing spaces with the '+' character and then using URL encoding on all other non-alphanumeric characters.
For TCP check types: