Host Tools automatically generates a unique access code for each guest's smart lock. You can also set a custom code for any reservation if you prefer.

If you are fully connected to Airbnb (have availability syncing enabled), Host Tools uses the last four digits of the guest's phone number for their door code. Airbnb now shares a guest phone number only when the listing is in the US or Canada and the guest lives in the same country as the host, and that number may be an Airbnb number that routes to the guest's phone. It is safest not to mention the guest's phone number and just use the {{Guest Lock Code}} tag in your messages, so the code they are given matches what is set on the lock.

For an Airbnb reservation without a phone number, Host Tools generates a unique code 5 minutes after the reservation is confirmed. The code is added to your lock ahead of the stay and appears in your messages wherever you use the {{Guest Lock Code}} tag.

From September 28, 2026, Booking.com no longer shares guests' phone numbers with connected software. For Booking.com reservations without a phone number, Host Tools generates a unique code as soon as the reservation arrives. That same code is added to your lock and appears in your messages wherever you use the {{Guest Lock Code}} tag, so the code your guest receives always matches the code on the lock.

Vrbo reservations usually include the guest's phone number. If a Vrbo reservation still has no phone number 5 minutes after it is confirmed, Host Tools generates a unique code for it in the same way. The code is added to your lock ahead of the stay and appears in your messages wherever you use the {{Guest Lock Code}} tag. Once a code is on the lock, it stays the same even if a phone number arrives later.

All generated codes are validated against your lock's specific constraints. For example, TTLock devices may not support certain digits, and Nuki locks cannot use codes that contain zeros or start with 12. Host Tools automatically adjusts the code to comply with these restrictions so guests always receive a working code.

You can override the auto-generated code with a custom access code for any reservation:

Host Tools will validate your custom code against your lock's constraints before saving. If the code doesn't meet the lock's requirements, you'll see an error message explaining which constraints were not met.

To include the guest's lock code in a message rule, use the {{Guest Lock Code}} tag. Here is an example:

KEY: There is a keypad attached to the front door. Your access code is {{Guest Lock Code}}, followed by the checkmark on the keypad. Please note that this code is not active until your scheduled check-in time. To lock the door when you leave just press any number.