Printing problems
Fix thermal receipt and PDF printing — Web Serial not supported, no serial port listed, garbled or blank receipts, receipts cut across pages, missing UPI QR and GSTIN.
Start with Printing & PDF for how printing works.
"Web Serial not supported in this browser — use the PDF receipt instead"#
Print thermal needs Chrome or Edge on a desktop or laptop. It does not work in Safari, Firefox, or on phones and tablets.
- Switch the counter computer to Chrome or Edge, or
- use Thermal preview and print the PDF through the printer's normal driver.
No port appears when you click Print thermal#
- Check the USB cable and that the printer is on.
- Install the printer's USB-to-serial driver from the manufacturer if Windows does not show a COM port.
- Close other software that uses the printer (another POS, a printer utility) — only one program can hold the port.
- Some printers connect only as a regular printer (USB printing class), not as a serial device. Use Thermal preview for those.
"Thermal print failed: …"#
| Cause | Fix |
|---|---|
| You closed the port chooser | Click Print thermal again and pick the port. |
| Port already in use | Close other programs using the printer; unplug and replug. |
| Printer switched off or out of paper | Fix and retry. |
Garbled characters or symbols#
The direct print sends ESC/POS commands at 9600 baud.
- Set the printer's serial speed to 9600 (usually via its self-test / DIP switches or utility).
- Make sure the printer is ESC/POS compatible.
- Otherwise print from Thermal preview.
Blank receipt#
- Thermal paper prints on one side only — flip the roll.
- Check the print head is not dirty and the paper is thermal, not plain.
Receipt printed on A4, or cut into pages#
Print Thermal preview with:
- paper size 80 mm (or "Roll paper 80 × 297"),
- scaling 100% / Actual size, not "Fit to page",
- margins None.
No UPI QR code#
Add a UPI ID in Settings → Invoicing. See Invoicing settings.
"GSTIN NOT SET — add it in Settings → Shop details" on the invoice#
Add your GSTIN in Shop details, then download the PDF again.
Old details on a reprinted invoice#
PDFs are generated when you download them, using your current shop details and template. Download again after changing settings.
"Download failed"#
The PDF could not be generated. Wait a moment and try again. If it keeps failing for one invoice, raise a ticket with the invoice number.
Related#
Last updated 15/09/2026