Complex situations:<p>- I&#x27;m logging in from a new computer. Maybe a computer I don&#x27;t trust enough to log in to my email (which controls nearly everything, as you note). Not all services are that important or need the same level of care as email.<p>- I&#x27;m a user that has greylisting enabled on my mail server, potentially delaying the email for several minutes.<p>Confusing:<p>- I&#x27;m a user that has never seen&#x2F;used this authentication workflow. While user&#x2F;pass is annoying, it is widely understood. Sometimes &quot;ease of use&quot; is really just &quot;what I&#x27;m used to&quot;. Thanks to facebook and Google authentication, the &quot;Login with...&quot; button is now &quot;what I&#x27;m used to&quot;. I&#x27;ve never seen the authentication method you&#x27;ve described in 20 years of web use, except as a password reset method.<p>Error-prone:<p>- Implementation would have to be done by me on all of my sites. There is no off-the-shelf plugin for this for Drupal or Wordpress or Mediawiki, which run 90% of the websites I am responsible for. I could develop it but I am certain I would make mistakes in said implementation. I should be clear that I think any form of authentication is error-prone, unless it&#x27;s already written and well-tested. User&#x2F;pass and optional email is already written and well-tested for every site I maintain.<p>Security:<p>- It forces login to email to login to your site. This increases the risk of a user logging in from an untrusted computer or in an untrusted location to an incredible degree.<p>- Also, one can easily add security questions, or other second factor, to a password reset form, to make it more secure than your solution. Password resets are rare; happening every year or two, most likely. Logins are daily. One cannot impose those security questions on daily login form without paying the same annoyance price as user&#x2F;pass (higher because it is unfamiliar). Cookies can mitigate this somewhat, but it doesn&#x27;t solve multiple devices, and security-conscious environments that don&#x27;t maintain cookies on logout.<p>If you believe this is an acceptable workflow for authentication, I won&#x27;t try to stop you. But, it simply isn&#x27;t a solution for my sites. I don&#x27;t like user&#x2F;pass, and I want something better, but I don&#x27;t believe what you&#x27;ve described is something better. It&#x27;s a neat idea, but not a solution to logins.