How to Fix – Rongta 80mm Thermal Printer – Firefox – ‘an unknown error occurred while printing’

Rongta 80mm Thermal printer is the most popular POS receipt printer in the world. It can run on a regular 80mm printer driver for windows. It is possible to print receipts from a web browser like firefox or chrome to Rongta printers. Although there are times, it might become hectic with different printing issues to send the printing data to the printer from the browser.

If you are trying to print your POS receipt from Firefox for a Rongta printer, a common problem, that appears time to time, is the following:

An unknown error occurred while printing

You probably failed to resolve the issue, even after uninstalling the Firefox or by Refreshing Firefox settings, or by clearing the printer saved settings on your browser. The issue is very weird. For some reason, Javascript’s window print fails to send the data to Printer through firefox, even though it thinks it did. I tried digging several things, but nothing worked until I found a way to actually make firefox think, it’s a new printer. Here are the steps you may following.

  1. Close the firefox, and make your Rongta 80mm printer the default printer of your system.
  2. Now open firefox, and type ‘about:support’ & enter.
  3. It will open a page. Scroll down to the printing section where it says Troubleshooting with ‘Clear saved print settings’. Click on the button to clear the settings.
  4. From the top press ‘Refresh Firefox’ button.
  5. Now restart your firefox, and type ‘about:config’. These is the firefox configurable environmental variables, that we wish to change some.
  6. Before we do, we first need to make firefox save, Rongta settings. One quick way of doing this is to open a new tab, browse, now go to Print from the File tab, it will show you ‘Advanced Preference’, now from the Print button at the top, make sure Rongta 80mm printer is selected and press Print. It will probably not print anything, but what it will help to do, is creating our printer settings in firefox.
  7. Now go back to the tab with ‘about:config’, at the top, type ‘print’ without quotes in the box that says ‘Search for preference’
  8. A lot of settings should appear, a couple of things you need to change.
  9. Delete print_printer or print.print_printer row.
  10. Set print.print_via_parent boolean value to ‘true’.
  11. Set print.tab_modal.enabled to ‘false’
  12. Make sure dom.enable_window_print this is set to ‘true’
  13. Make sure print.show_print_progress is set to ‘true’
  14. Now, close the window, and restart your firefox again.

You should now be able to print your POS receipt using Rongta 80mm printer using Firefox.