Some of the services I make have "private urls" and/or a cookie containing a token to auto-login you so you can use it without an account. But it works only if:

Some of the services I make have "private urls" and/or a cookie containing a token to auto-login you so you can use it without an account. But it works only if: - the data are not very sensitive. It's very easy to mess with. - people are tech savvy enough to understand what a URL is or never get in a situation where they don't have the cookie - your service is too small to attract spammers - you can setup a decent system to prevent bot from creating accounts It's hard, plenty of gotchas, and just satisfied a minority of privacy-minded users. Though to sell.