According to the official AO3 FAQ on Accessing Fanworks, the following are official and safe URLs: (Primary Domain)
Sometimes a specific Internet Service Provider (ISP) has trouble routing traffic to the primary domain. Official AO3 Mirror and Alternative Links ao3 mirror link
In this guide, we’ll explain what AO3 mirrors are, which ones are safe to use, and how to stay connected to the archive when the main domain is acting up. What is an AO3 Mirror Link? According to the official AO3 FAQ on Accessing