Written for Synergy 3 (v3.8.4) and Synergy 1 (v1.22.3), checked 20 October 2026.
Enter your serial key on every computer in your setup. Only the primary computer in Synergy 3, or the server in Synergy 1, uses an activation, but each computer needs the key.
Your serial key is on your account page, under Licenses. Synergy 3 takes the key of a Synergy 3 Lite, Synergy 3 Plus, Synergy 3 Max or Synergy Business license, and Synergy 1 the key of a Synergy 1 or Synergy Business license. For how to find and copy it, see: Finding your serial key and license details on your account
Upgraded, renewed or finished a trial? Enter your new serial key on every computer, as below. An upgrade (for example from Synergy 3 Lite to Synergy 3 Plus, or from Synergy 1 Basic to Synergy 1 Pro), a renewal of your business subscription, or a Synergy Business trial turning into a paid business subscription puts a new serial key on your account, and neither Synergy 1 nor Synergy 3 picks it up on its own. A trial key stops working when the trial ends.
Entering your key or logging in doesn't use an activation by itself; your license activates when the Synergy 3 primary computer next starts sharing, or when you next click Start on the Synergy 1 server. How activation works, including offline serial keys: How license activation works
Synergy 3
To start, click License in the left sidebar of Synergy 3. The Apply new license page opens, with two ways to update. Either way, Synergy 3 can send the key to your other computers for you with Update all computers.
Log in to your account
- Click Update using Synergy account.
- Type your Email and Password.
- Click Update all computers, or Update this computer to change only this one.
Synergy 3 fetches the serial key from your account for you, an offline serial key included. If your account has more than one license, it takes your Synergy Business license first, then your highest Synergy 3 edition. An offline key then activates on the primary computer with an activation code and a response code. For the steps, see: How license activation works
Paste your serial key
- Copy your serial key from your account page.
- In Synergy 3, click Update serial key manually.
- Paste your serial key.
- Click Update all computers, or Update this computer.
Update all computers reaches the computers Synergy 3 is connected to at the time. If a computer was offline, repeat the steps on it.
The first time you open Synergy 3
The Welcome to Synergy 3 screen offers the same two ways, for that computer only. Click Continue to login, type your Email and Password, and click Log in. Or click Use serial key manually, paste your serial key and click Continue.
If Synergy 3 shows a license message
Click Apply new license on the message, then log in or paste your serial key as above. Synergy 3 shows a message when there's something to do about your license, for example Your license is invalid. when it can't read the serial key it has stored, or a warning before a Synergy Business license or trial ends. What each message means: License messages
If your login or serial key isn't accepted
- Invalid email address or password. Log in with the email address you bought with, or click Forgot your password? to reset your password.
- Sorry, there are no valid licenses on your account. Log in with the account that holds your Synergy 3 or Synergy Business license. A Synergy 1 license doesn't work in Synergy 3; to move to Synergy 3, see: Upgrade your license to a higher edition or to Synergy 3
- Sorry, there was a problem logging in. Paste your serial key instead, as above. This message shows when the computer can't reach our server to log in, for example because its network blocks it.
- Invalid serial key. Please log in to your Synergy account to get the correct one. Copy the whole serial key of your Synergy 3 or Synergy Business license again from your account page and paste it in, or log in to your account instead.
Synergy 1
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... (on macOS, Synergy > 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.
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 verifying your computers
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 Exit; click Back there to go back and enter a key.
When your license or trial is ending
Renew your business subscription, or buy a license when your trial ends, then enter your new serial key in the window that follows the warning. Once the license has expired, Synergy 1 stops working until you enter a valid key, and the Serial key window opens by itself when Synergy 1 starts. What each warning says: License messages
If your serial key isn't accepted
- Invalid serial key. Copy the whole serial key of your Synergy 1 or Synergy Business license (not a Synergy 3 one) from your account page and paste it in. On Synergy 1 (v1.17 and earlier) that won't help, so update instead: Older Synergy 1 says Invalid serial key?
- Sorry, that serial key has expired. Renew your license, then enter the new key.
- The settings file is not writable, in a Write access required message. Ask your administrator, or check the permissions of the file named in the message. Synergy 1 can't open the Serial key window until it can write to that file.
Older Synergy 1 says Invalid serial key?
Update to the latest Synergy 1, then enter your key again. For the download, see: Downloading the latest or an older version
Synergy 1 (v1.17 and earlier) can't read our newer serial keys, so it rejects a valid one. To check your version, see: Finding which version you're running
Can't update, for example because the latest Synergy 1 doesn't run on your operating system?
- For business and enterprise customers: we build the latest Synergy 1 for any system its vendor still supports. That covers standard support on every business license, and paid extended support too on Synergy Business Advanced or Synergy Enterprise. Otherwise, we'll send you a serial key your version reads. To ask for a build or a key: Contact our business team
- For personal, non-commercial customers: if your system still has its vendor's standard support, we'll build the latest Synergy 1 for it; otherwise, we'll send you a serial key your version reads. To ask for a build or a key: Contact support
Which systems the latest Synergy 1 runs on: Operating system and hardware requirements
What each older version shows:
- Synergy 1 (v1.17): Invalid serial key. Please contact us for help. Newer versions show the same message for a mistyped key, so check your version first.
- Synergy 1 (v1.15 and v1.16): Sorry, a fatal error has occurred and the application must now exit. The error under it mentions invalid serial key version, and Synergy 1 closes when you click Abort.
- Synergy 1 (v1.8.5 to v1.14.6): An error occurred while trying to activate Synergy. The message ends with Invalid serial key.