How to change a key safe code

Before you start

• You need the current code. On almost every key safe, the code can only be changed while the safe is open.
• Keep the door open until the new code works. Test it several times with the door open. If you close it on a code you set wrong, you may not get back in.
• Have your model's instructions to hand. They are often printed on a card inside the lid. If not, search for the model name on the front of the safe.
• Take the key out first if you are not sure, so a mistake never locks the key in.

Dial key safes (for example, Master Lock 5401D)

These have a row of number wheels you turn and a reset lever on the inside of the door.

1. Turn the wheels to the current code and open the door. A new Master Lock 5400D or 5401D is set to 0-0-0-0.
2. On the inside of the door, find the reset lever. On the 5400D and 5401D, push it left and down; it stays in that position.
3. Turn the wheels to your new four-digit code.
4. Push the reset lever back to its original position, back and to the right. The new code is now set.
5. With the door still open, scramble the wheels, enter the new code and check the door opens. Do it more than once.
6. Close the door and scramble the wheels.

Other dial models, and other versions of the 5401, can have the lever elsewhere or move it the other way. If yours looks different, follow the instruction card inside the door.

Push-button key safes (for example, Supra C500)

These have 12 buttons with numbers and letters, a CLEAR button and an OPEN handle. The code is the set of buttons that are switched on, so the order you press them in does not matter. There is no master or reset code, so write your new code down somewhere safe before you start.

1. Pull open the weather cover, press CLEAR, enter the current code and turn the OPEN handle 180° clockwise to open the lid.
2. Slide the white plastic card off the back of the lid. It is the code change tool.
3. With the lid still open, turn the OPEN handle 180° anticlockwise, back to the locked position. The word OPEN reads the right way up again, and a green triangle shows on the locking bolt. Changing the code with the bolt down can damage the safe.
4. On the back of the lid, each button has a grey dial with a small arrow. Pointing towards the hinge means the button is ON (part of the code); pointing away from the hinge means it is OFF.
5. With the card, never a screwdriver, turn every dial to OFF. The OPEN handle should now turn without a code; check it, then turn it back to locked.
6. For each button in your new code, turn its dial 180° until the button pops fully back up and the arrow points towards the hinge.
7. Test with the lid still open: press CLEAR, press only your code buttons until each one clicks, and turn the OPEN handle. It should turn fully and the bolt should pull back.
8. Put the card back on the lid. To lock, close the lid and turn the OPEN handle 180° anticlockwise, back to the locked position.

When to change the code if you host guests

A key safe code is only as private as the last person who knew it. For a holiday let or short-term rental, the safest habit is simple: one code per stay.

Choosing a good code

• Avoid the obvious: 0000, 1234, the house number, a year.
• Don't reuse the same code across properties or for your own front door.
• On push-button safes, use more buttons. The Key Safe Company suggests five to seven, mixing numbers and letters. Each button can only be used once.
• Write it down somewhere private, not on the safe or under the doormat.

Telling guests the new code

Send it privately and close to arrival. Never put it in your listing, your Instagram or any page that anyone can open. Copy this message and fill in the brackets:

Hi [Guest name],

Your stay at [Property name] starts tomorrow. Here's how to get in.

The key safe is [where, e.g. "to the left of the front door, behind the planter"].
Code: [code]
Press [CLEAR / the reset button] first, enter the code, then turn the handle.

Please put the key back in the safe and scramble the code when you leave.

Any problem, call or message me on [phone].
[Your name]

The trouble with sending codes in messages is that they stay there. A gstl.ink private page keeps the code, WiFi and check-in details on one page that only your current guest has the link to. Change the code on the page once, and rotate the link between stays with one tap: the previous guest's link stops working, and the page translates itself into your guest's language.

Mistakes to avoid

• Closing the door before testing. The most common way to lock yourself out of your own key safe.
• Leaving the wheels on the code. Always scramble a dial safe after closing it.
• One code forever. Every guest you have ever hosted could still open it.
• The code in a photo. Check that pictures of your entrance don't show the safe open or the wheels set.

Writing the rest of your arrival message? The check-in and check-out instructions guide has templates for self check-in and late arrivals.

Sources

• Master Lock, "Reset & Retrieve Lost Combinations", section for the 5400D / 5401D Key Safe, read on 20 October 2026.
• The Key Safe Company (Supra UK), "Code Change Guide – C500 KeySafe" (PDF), read on 20 October 2026.