Mech Arena has official events, store offers and Plarium account rewards, but public code lists can go stale quickly. This hub does not mark unverified third-party codes as active.
The safest places to check are the in-game event panel, the official Mech Arena site, Plarium Play, the official Plarium Store and official social channels. If a code or offer asks for account details outside official Plarium properties, treat it as unsafe.