For many users, the free version of AirDroid is sufficient. It allows for file transfers, notification mirroring, and SMS management over a local network without a subscription.
Phishing attempts to get you to log in to a fake AirDroid portal. The Safe Way to Get AirDroid Premium
You may find websites listing "AirDroid Premium activation codes." In reality, AirDroid typically uses a tied to an email account rather than a one-time license key system for individual users. Most "keys" found on forum threads or YouTube descriptions are either: Expired promotional codes.
Most "working" cracks are outdated. AirDroid uses server-side verification for its premium features. This means that even if an app looks like the premium version, the features (like the 200MB file limit) often won't work because the server doesn't recognize your account as valid [1].
AirDroid’s developers monitor for irregular activity. Using a modified application can lead to your account being permanently banned, losing you access to your synced data and devices.