# Registering DU Meter

The Register DU Meter window turns your copy of DU Meter from a trial into a licensed one. Open it with
**Register** in the [pop-up menu](https://www.hageltech.com/support/kb/du/using/menu), which is there until DU Meter is registered.

### Buy DU Meter

Opens the DU Meter purchase page in your browser. Your user name and serial number arrive by e-mail, usually
within minutes. If you have a license for an earlier version of DU Meter, the window offers **Upgrade DU
Meter** instead, which opens the upgrade page: see [What is DU Meter upgrade policy and how do I upgrade?](https://www.hageltech.com/support/kb/du/upgrade_policy) for what an upgrade costs.

If the page does not open, the window shows its address, which is also on your clipboard: paste it into your
browser.

### Enter your serial number

Enter the user name and the serial number exactly as your order confirmation e-mail shows them, and click
**Register**. Copying both from the e-mail is the surest way: see [How to copy and paste your serial number](https://www.hageltech.com/support/kb/du/using/serial).

If the window says the two do not match, or that the serial number is for an earlier version of DU Meter,
[Registration problems](https://www.hageltech.com/support/kb/du/registration_problems) explains what to do. **Lost your serial number?** opens the page where you can
have it sent to you again.