As this answer on Stackoverflow states.

https://httpbin.org/ allows you to echo back your request, to see that it does what you expect.

this is the list of services

It echoes the data used in your request for any of these types:

• https://httpbin.org/anything Returns most of the below.
• https://httpbin.org/ip Returns Origin IP.
• https://httpbin.org/user-agent Returns user-agent.
• https://httpbin.org/headers Returns header dict.
• https://httpbin.org/get Returns GET data.
• https://httpbin.org/post Returns POST data.
• https://httpbin.org/put Returns PUT data.
• https://httpbin.org/delete Returns DELETE data
• https://httpbin.org/gzip Returns gzip-encoded data.
• https://httpbin.org/status/:code Returns given HTTP Status code.
• https://httpbin.org/response-headers?key=val Returns given response headers.
• https://httpbin.org/redirect/:n 302 Redirects n times.
• https://httpbin.org/relative-redirect/:n 302 Relative redirects n times.
• https://httpbin.org/cookies Returns cookie data.
• https://httpbin.org/cookies/set/:name/:value Sets a simple cookie.
• https://httpbin.org/basic-auth/:user/:passwd Challenges HTTPBasic Auth.
• https://httpbin.org/hidden-basic-auth/:user/:passwd 404'd BasicAuth.
• https://httpbin.org/digest-auth/:qop/:user/:passwd Challenges HTTP Digest Auth.
• https://httpbin.org/stream/:n Streams n–100 lines.
• https://httpbin.org/delay/:n Delays responding for n–10 seconds.