Why do I have to click again to confirm I want to unsubscribe from the newsletter?

While we could make it so that clicking the link in your email would immediately unsubscribe you, it would be in violation of internet standards. Specifically, the HTTP protocol’s GET method definition which states that:

NOTE
GET requests should only retrieve data and should have no other effect.

wikipedia.org/wiki/HTTP#HTTP/1.1_request_messages

A GET request is what happens when you follow a link. Merely following a link should not make any changes (like unsubscribing you from a newsletter).

For example, when you receive an email, your email client may preload the links in it in the background. So that they are quicker to load should you click on them.

Obviously, this preloading should not unsubscribe you. Which is why you need to click a button to confirm. Because that will trigger a POST request and those can make changes.

TIP
This does not apply to users unsubscribing through their account

None of this applies to users who unsubscribe from our newsletter by disabling the option in their account. In this case, you are already clicking a button, rather than a link in your email.

If you are curious, we use an idempotent PUT request under the hood.

Why do I have to click again to confirm I want to subscribe after I already clicked the confirmation link you sent me?Where did the "standard" measurements go?