Hey ​@Alessandra_Ciancio, thank you for reaching out! 

Yes, you can share your prototype with anyone using Share Prototype > Anyone with the link > Can view, which allows access without requiring a login. However, this setting makes the prototype accessible to anyone with the link, rather than restricting it to specific email invites.

If you’d like to share it with invites only, it might require a login. You can find more details in our Help Center article here: Figma Help Center.

Hope this helps! Let me know if you have any other questions.

Hey! Thanks for your replay.

In this way anyone can access either in the file.

My needs are that:

• in the prototype anyone can view,
• in the file only invited emails can access.

I should differentiate the type of permissions. Is it possible?

Hey ​@Alessandra_Ciancio! Yes, this should be possible.
If you want to anyone to view your prototype with a link but only invited users be able to access your file, you need to adjust the share setting in your file separately. See screenshot:  

And also as mentioned before, Share Prototype > Anyone with the link > Can view, which allows access without requiring a login.

Please let me know if this is clear, happy to help out further! 

I get it! In the prototype I was seeing the option disabled because I had already set Anyone in the file. If I set in the file only email invited instead, the option is enabled in the prototype.
Thanks :)