Written for Synergy 1 (v1.21.4), checked 3 October 2026.
Enter your serial key on every computer in your setup. Only the server uses an activation, but each computer needs the key. Copy it from your account page: Your account
Enter or change your serial key
- In Synergy 1, choose License > Change serial key.
- Paste the key into Enter your serial key.
- Click OK.
You can also open the same window from Help > About Synergy..., with Change next to your key.
Synergy 1 confirms with Thanks for entering your serial key and the edition, which also appears in the window title. Do this on every computer, with the same key: with encryption on, Synergy 1 reminds you that using the same key everywhere keeps TLS working.
Entering the key doesn't activate it. Your license activates on the server the next time you click Start. How activation works, including offline keys: How license activation works in Synergy 1 and Synergy 3
After an upgrade or a trial
Enter your new serial key on every computer, as above. An upgrade (for example from Synergy 1 Basic to Synergy 1 Pro), or a Synergy Business trial turning into a paid subscription, puts a new serial key on your account, and Synergy 1 doesn't download it for you. A trial key stops working when the trial ends; if it already has, the Serial key window opens by itself when Synergy 1 starts.
Synergy 1 Pro adds TLS encryption. If it isn't on after you upgrade, turn it on, on every computer. For the steps, see: Encryption and fingerprints in Synergy 1
The first time you open Synergy 1
The Serial key window opens by itself when Synergy 1 has no valid key, and again if you click Start without one. Its links take you to your account page, to Purchase a license, or to Request an offline key for computers without internet access. If you click Cancel, Synergy 1 explains that you need a license and closes when you click OK; click Cancel there to go back and enter a key.
When your license or trial is ending
Synergy 1 warns you before a subscription or trial ends, with License expiring soon, and again with License expired. Renew, then enter your new serial key in the window that follows. When the license has expired, Synergy 1 stops working until you enter a valid key.
If your key isn't accepted
- Invalid serial key. Copy the whole key again from your account page and paste it in.
- Sorry, that serial key has expired. Renew your license, then enter the new key.
- Write access required: Synergy 1 can't save the key because the settings file named in the message is read-only. Ask your administrator, or check the file's permissions.
Using Synergy 3? See: Enter or change your serial key in Synergy 3