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Choose Free or Pro
Start with installation and first connection. Local debugging needs no account or payment.
- Free: up to 16 serial, TCP or UDP connections, bridges, projects, settings sync, text/Hex views, checksums and local logs, without a paid license. The Modbus request builder, X/YMODEM, auto reply, sequences, scripts, plot, protocol decode, export and replay are included with per-session allowances; see the Free and Pro comparison.
- Pro: removes those allowances and keeps a 1,000-entry send history across computers. Personal and Enterprise licenses unlock the same Pro tools; Enterprise supports organization purchasing and offline activation.
- No trial needed: Free has no time limit. Buy a license when you need Pro; saved project files and logs are always kept. A trial still running when you upgrade to 6.6.8 lasts until 30 days after installation; new installations start as Free. The Mac App Store subscription has no introductory offer; its price is shown in the app.
- Remote access: RFC 2217 client and quick sharing, Live Console, Live Relay and Live Share are available in Free. Cloud accounts have a traffic allowance; invited guests can join without an account. See current allowances and traffic metering. Online features (sign-in, license activation, cloud services) start after you allow them in the first-start dialog; Help > Privacy and Online Features… changes the choice.
- Deleting your account: in the account center choose Delete account, or in the application Cloud > Delete Account…. Deletion is immediate; license keys stay valid and are released from the account. See the Privacy Policy.
Purchase and receive a license
- Compare Personal and Enterprise prices. Personal offers 1 month, 1 year, 3 years and lifetime; Enterprise offers 1 year, 3 years and lifetime.
- Choose WeChat Pay for CNY or PayPal for USD. Confirm the edition, term, quantity, delivery email and final total. Website term licenses do not renew automatically.
- Decide whether to bind the key to the delivery email's account. Binding defaults on for Personal and off for Enterprise. A key binds to one account; it cannot be moved to another account through self-service.
- Complete payment. Use the delivery email and receipt to activate. A created order or a return from the payment provider is not by itself proof of successful payment; check the confirmed order status.
Bought the wrong thing, or no longer need it: an order paid within the last 14 days whose keys have not been activated can be refunded from Dashboard > Orders. Request a refund has the steps and the conditions.
Mac App Store subscriptions use the Apple Account, price and renewal terms shown in the app. Use Restore Purchases on a Mac signed in to the same Apple Account. An existing website key can be entered through Enter License Key in current App Store builds; do not buy a second license just to switch distribution channels.
Activate and return to SPU
For what each step looks like in the application -- registering an account, signing in, pasting a key, offline activation -- see the illustrated Register and activate guide. The table gives the next step for each purchase situation.
| Purchase or device situation | Next step |
|---|---|
| Key bound at checkout; account already exists | Sign in to SPU with the delivery email. The account activates this machine automatically. |
| Key reserved for an email without an account | Register and verify an Alithon account with that exact email, then sign in to SPU. |
| Key not bound at checkout | In current desktop builds, sign in, open Help > License Management, enter the key and activate. Binding is optional; online sign-in and permanent key binding are different actions. |
| Enterprise device without internet | On that device, open License Management > Offline Activate and copy its CID. On another internet-connected computer, open offline activation, enter the CID and Enterprise key, and bring the generated activation code back to the device. |
| App Store subscription | Use Restore Purchases with the purchasing Apple Account. An Alithon email alone does not restore an Apple purchase. |
Check the license status and expiry in SPU, then return to the task. Personal account-bound keys follow the owner's signed-in computers; unbound Personal keys have a concurrent-device limit. Enterprise follows its purchased seat count whether bound or not. Signing out releases a bound key on that machine; it does not remove an unbound key. See account binding and device limits.
If payment or activation seems stuck
- Check the delivery address, spam folder and confirmed payment status. Use the channel-specific lookup under Purchase and activation or your account's order history before placing another order.
- For a bound key, confirm SPU uses the same email as the purchase. If you entered the wrong address or bound to the wrong account, contact support with the order number; do not share account credentials.
- If the device limit is reached, release an old device from your license dashboard. If the license is expired, renew before retrying Pro features.
- For offline activation, use an Enterprise key and the CID from the target computer, not the internet-connected computer.
- If sign-in, key entry or restore fails, update to the latest compatible build and include the displayed error in your support request.
Before contacting support
Please include as much of this information as possible:
- On Serial Port Utility 6.6.8 or later, Help → Export Diagnostic Pack… collects the version, system, serial port list, port settings and recent data into one
.zip— attach it instead of gathering the items below by hand. It never contains your licence key, account or machine ID (CID); see the diagnostic pack. - Operating system and Serial Port Utility version.
- Device model, adapter model and driver name.
- Serial parameters: port, baud rate, data bits, stop bits, parity and flow control.
- Text or Hex mode, Append Line Ending and Enter Sends settings, and the exact command you sent.
- Screenshot of the connection state and Rx/Tx counters.
- A short log file or sample frames showing both request and response.
- For orders or activation: order number, checkout email, CID and license type.