While working on a project, we’ve had to compare two curl requests that both returned a web html page. Instead of saving two tmp files for each curl and then diff the two files, diff allows us to use the following expression:

diff <(command_1) <(command_2)

In this way, to be diffing two curl responses we can use:

diff <(curl url) <(curl url)

Note that curl’s --silent flag can be useful here, see documentation

-s, --silent Silent or quiet mode. Don't show progress meter or error messages. Makes Curl mute. It will still output the data you ask for, potentially even to the terminal/stdout unless you redirect it.