They still need to log in. Why do you state otherwise? Or is this different with different versions of Jira server?

[BlueHat Dave]

This question is in reference to Atlassian Documentation: Allowing anonymous access to your project

In particular, I would find it very useful to allow completely anonymous access to (only) view projects and issues.

[Nic Brough -Adaptavist- · Accepted solution]

I think you've misread the documentation.

You do not need to log in to JIRA to get anonymous access.  As long as you (the admin) has set up the permissions correctly, as per doc.

[BlueHat Dave]

And the difficulty was multiple layers of permissions; you need to have "None" be an option in the Issue Security Scheme, and also have the Security field in the Field Configuration set to "Optional".

[Nic Brough -Adaptavist-]

Yes, setting your security level to mandatory is, of course, going to stop anonymous access.  Of course, that's not a default, it's something you have to do deliberately.