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Install QZ Tray

Install QZ Tray on the computer that prints and authorize La Comanda with the certificate so it never asks for permission again.

Updated on October 9, 2026

The browser cannot talk directly to a thermal printer. QZ Tray is the free application that receives the ticket inside the same computer and sends it to the printer you picked; nothing goes out to the internet. It is installed once on each computer that will print and takes about ten minutes.

Before you start

  • You need a computer running macOS, Windows or Linux. Tablets and phones cannot print thermal tickets.
  • The printer must be installed in the operating system. The short rule: if your computer can already print a test page on that printer, La Comanda can too. If you are unsure about your model or connection, check Compatible printers.

Step 1: install QZ Tray

  1. Download QZ Tray from qz.io/download and install it like any other program.
  2. Confirm it is running. When it finishes, QZ Tray stays in the background: look for its icon in the menu bar on Mac or in the system tray on Windows, next to the clock (it may be under the ^ arrow). If it is not open, nothing can print.

QZ Tray listens locally on ports 8181, 8282, 8383 and 8484, and on 8182, 8283, 8384 and 8485. If your antivirus or firewall asks, allow it: this is traffic inside the same computer and never leaves your network.

Step 2: authorize La Comanda

Out of the box, QZ Tray shows a security prompt every time something wants to print. This step installs a certificate that tells it to trust La Comanda, so the prompt never comes back.

  1. Open Settings → Point of sale (/admin/settings/pos) and scroll to the Printer card.
  2. Press Setup wizard. The wizard detects your operating system.
  3. Mark I've installed QZ Tray to move on to the certificate.
  4. Press Download installer and run it. It depends on the system:
    • macOS: download "La Comanda Printer Setup.pkg". Double-click it, press Continue and then Install, and type your Mac password. You can also use the Terminal option: Copy command, paste it into the Terminal app and wait for the "Printer setup complete" message.
    • Windows: download setup-printer.bat and double-click it from Downloads. If the SmartScreen warning appears, press More info and Run anyway; in the blue User Account Control box, Yes. It is done when you see "Printer setup complete".
    • Linux: Copy command, paste it into a terminal with Ctrl+Shift+V, press Enter and type your password. The script uses pkexec when there is a graphical session and sudo otherwise, and expects QZ Tray under /opt/qz-tray.
  5. Mark I ran the installer and press Test connection. It should say Connection successful! and then All set!.

Why does it ask for a password? The certificate is copied into the QZ Tray folder, which is protected by the system. The password authorizes that single file copy; nothing is sent to the internet.

The same installers are on the public printer guide, in case you prefer to download them without going into the admin panel. Every installer first checks that QZ Tray is installed and, when it finishes, restarts it with the certificate loaded.

Step 3: reopen QZ Tray if it keeps asking

QZ Tray only reads the certificate when it starts. The installer restarts it for you, but if the prompt still appears when printing, quit it from its icon (right-click › Exit on Windows, Quit in the Mac menu bar), open it again and reload the La Comanda page. To confirm the certificate is in place: right-click QZ Tray › Advanced › Diagnostic › Browse App folder…; that folder must contain the file override.crt.

If QZ Tray shows its prompt

With the certificate installed, the prompt says Verified and choosing Allow once is enough; it does not come back. If you see it without "Verified", the certificate is not on that computer: repeat step 2.

Never choose Block with Remember this decision checked. Without the certificate, checking that box disables Allow, so the only answer QZ Tray can remember is Block; it saves it in the user's folder, and neither reinstalling QZ Tray nor restarting the computer clears it. If it already happened, the block is removed in QZ Tray itself: right-click its icon › Advanced › Site Manager… › Blocked tab, select "La Comanda (La Comanda POS)" and press −. The complete unblock, step by step, is in Printing troubleshooting.

Next step

With QZ Tray authorized, pick your printers and paper size in Set up your printer.

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