Atlassian update - August 2024
Thankyou for sending through your feedback.
Currently, the restriction is in place due to security considerations and compatibility issues. Unfortunately, we don't have any plans on working on this idea. However, your feedback has been shared with our development team for further evaluation.

In the meantime, here are some workarounds you might consider:

• Alternative Characters: Use hyphens or other valid characters in place of underscores in the Base URL.

• Custom Domain: Consider setting up a custom domain that adheres to the current URL restrictions.

• Proxy Configuration: If running behind a proxy, ensure the proxy name matches the Base URL without underscores.

If you have further questions or need additional support, please feel free to reach out. We appreciate your understanding and patience as we work to improve our products.

Best regards,
Joe Nguyen
jnguyen2@atlassian.com
Product Manager - Jira Cloud

Today is not possible to use underscore in JIRA's Base URL. When we try to use it, the "You must set a valid base URL." error appears.

I believe it blocks underscores due to this bug in the Activity Stream, however, since the underscore is a valid and unreserved character as per the RFC 3986, it should be great if we can use it.