Fix: New Usernames Cannot Contain Certain Special Characters

A bug was reported where new user registration fails when the username contains certain characters, including the special "O" character (Ø) and other non-ASCII characters.

Symptoms

• Registration form rejects valid usernames containing special characters
• Error message: "Invalid characters in username" even for valid characters
• Affects users with names from Scandinavian and Eastern European languages

Cause

The username validation regex was too restrictive, blocking valid Unicode characters that should be permitted in usernames under the configured locale.

Fix

This issue is resolved in APG vNext 4.4, which updated the username validation to properly handle Unicode character ranges:

• Upgrade to APG vNext 4.4 for the permanent fix — see release notes.
• As a workaround on older versions, modify the username regex in Admin Panel → Settings → Registration to use a more permissive Unicode-aware pattern.

Post questions in the Support Forum.

Username Character Validation in APG vNext

When users report that certain characters are not accepted in usernames during registration, the cause is typically the username validation regex configured in APG vNext's registration settings, or a database collation issue that cannot store the submitted characters. Understanding both sources of the problem is necessary to fix it correctly for all affected users on the forum platform.

Default Validation Rules

APG vNext's default username regex accepts alphanumeric characters and a limited set of safe special characters including hyphens, underscores, and periods. Spaces, HTML special characters, and certain Unicode characters outside ASCII may be excluded by the default pattern. The rejection of common characters like accented letters indicates either the validation regex is too restrictive or the SQL Server database collation does not support the Unicode range needed.

SQL Server Collation

Verify the SQL Server database collation supports full Unicode by confirming it uses a collation with _CI_AS suffix or an appropriate Unicode-supporting collation for your language. If the database was created with a non-Unicode collation, migrating to a Unicode-compatible collation may be required to support the full range of international characters in usernames.

Updating the Validation Regex

To allow additional characters in usernames, update the validation regex in Admin > Registration Settings. Test the updated regex thoroughly before deploying to ensure it does not allow characters that would cause security issues such as HTML injection in username display, SQL injection vulnerabilities, or URL encoding problems in user profile pages where the username appears as part of the URL path structure.

Looking for more help? Browse the support forum or check the Knowledge Base.