Are there common situations that cause a "401 Error" being displayed without a login dialog being displayed first?

Solution 1:

A few things to try or consider:

• Are you serving these pages securely? There is a GPO and Google Workspace setting that only allows basic auth using HTTPS - GPO, Chrome Policy

• Do the credentials to the URLs change reasonably frequently? It could be possible the user hasn't closed/restarted their browser since their last successful login and subsequently the credential change causing the httpauth cache to be incorrect and cause the issue.

• There are some auth settings in the Windows Internet Options dialog that apply to Chrome and IE that could cause an attempted automatic login.

• Are there any password managers that can autofil the login dialog?

• Just did a few quick tests with some online proxies and a HTTP basic auth prompt with mixed results. Some refused to load the page, some presented their own login prompt and some used the built in browser prompt. It suggests that a misconfigured proxy could cause no login prompt to appear.