Browse the docs

Label printing

Roll labels print straight to the Zebra label printer through Zebra Browser Print, a small helper app on the same computer as the browser. When the browser can't reach it, Twin Check'n falls back to a PDF so you can still print something.

Symptom: "Browser Print agent is not reachable"

You select Print Labels, a small Label Printer window opens with "Browser Print agent is not reachable," and then a PDF of the labels opens in a new tab. Nothing goes to the Zebra printer.

This is almost always a certificate that the browser has stopped trusting, not a problem with the app. Twin Check'n talks to Browser Print at https://127.0.0.1:9101, which uses a self-signed certificate. The browser refuses to connect until you accept it, once per browser. Browser updates, cleared browsing data, a new browser or a new profile all reset that.

The fix: accept the certificate

Do this in the same browser you use for check-in.

  1. Make sure Zebra Browser Print is running. Look for its icon in the system tray (Windows) or menu bar (Mac). If it isn't running, open it and wait a few seconds.
  2. Open a new tab and go to https://127.0.0.1:9101/ssl_certificate.
  3. The browser warns that the connection isn't private. Continue anyway:
    • Chrome / Edge: Advanced → Proceed to 127.0.0.1 (unsafe)
    • Safari: Show Details → visit this website → Visit Website
    • Firefox: Advanced → Accept the Risk and Continue
  4. You should see a short reply from Browser Print instead of an error.
  5. Go back to Twin Check'n and print again. If the order was already checked in (check-in happens on Print Labels & Check In even when the labels fall back to a PDF), reprint from the order window on Orders with Print All Labels.

Still not working?

Work through these in order:

  1. Is Browser Print running? Open https://127.0.0.1:9101. A certificate warning means accept it (above). "Can't connect" means Browser Print isn't running. Start it.
  2. Is the printer set as default? In the Browser Print app, the Zebra printer should be listed and set as the default device. "No Zebra printers found" means you need to add it there.
  3. Are you on the right computer? Browser Print must be on the same computer as the browser. It won't work from a tablet, phone or another computer.
  4. Did something reset the trust? Repeat the certificate steps after any browser update, or in any new browser or profile.

Printing a PDF on purpose

If the Zebra printer is out of action, select Print as PDF instead in the Label Printer window to go straight to a printable PDF.

Out of label stock

If the lab has run out of roll labels but still has pre-printed barcode labels, an admin can turn on Pre-printed label mode in Settings → Labels. Check-in then asks you to scan a pre-printed label for each roll instead of printing one. See Checking in with pre-printed labels.

Labels print, but look wrong

Size, spacing, text size and darkness are set in Settings → Labels. If labels drift across a multi-column roll, re-measure the column spacing as described there.

PreviousStaff