JSI Tip 3447. What is the maximum length of a fully qualified Active Directory domain name?

Windows 2000 permits file paths, including UNC paths, to be 260 characters in length. This MAX_PATH limit is can quickly be exceeded when using Group Policies, which references files in the SYSVOL using UNC paths. A typical UNC path used by Group Policy would be similar to:

\sysvolPolicies

If the length of the Group Policy UNC exceeds the MAX_PATH, the policy cannot be read and applied.

The fully qualify Active Directory DNS domain name is limited to less than 64 ASCII characters to avoid these problems.

NOTE: Some languages, such as Japanese, are further limited, as one of their characters may take up to 3 bytes.