Question

Im interested in a way one service activate users. The scenario is that I filled form and sent it. Then there was a message that if I want to continue activation process I should check my email. In the email there was a message iwth activation link like: http://www.theservice.com

I wonder how they know that it was me 🙂

I know scenario in which link which is sent contains hash of users login or something so that server knows which user enters and activates that one.

Do you know how it can be done ?

EDIT:

According to answers: Strange thing is that I dont have a token in my link which I received. Link is simply http://www.myservice.com and despite of that this service is still able to activate my account.

The only thinkg that I can imagine how it works is the cookie.

Answer 1

The mail message may contain an html with form and a hidden field inside it for user id. When user click on the link form submitted on appropriated server where hidden field value retrieved for recognizing user id and following account activation.

function doSubmit() {
        document.forms["form1"].submit();
    }

<form id="form1" action="www.theservice.com" method="post">
    <a href="#" onclick="doSubmit()">Activate</a>
    <input type="hidden" name="userIdForActivating" value="userId" />
</form>