When printing Royal Mail 2D barcodes with the Zebra GK420D printer you need to make sure that you have your dithering set to none.
This is important as it ensures a crisp scannable barcode is produced so that Royal Mail's delivery confirmation features can be used.
- Understand why dithering must be disabled
When printing Royal Mail 2D barcodes on the Zebra GK420D, the dithering setting must be set to None. Dithering distorts the barcode image, making it blurry and unscannable. Disabling it ensures a crisp, clean barcode that Royal Mail's delivery confirmation system can read reliably.
- Open Control Panel and navigate to Devices and Printers
Navigate to your Control Panel and click View devices and printers. This will show you a list of all printers installed on your computer, including your Zebra GK420D.
- Open Print Properties for the Zebra GK420D
Right-click on your Zebra GK420D printer in the list and select Print properties from the options that appear. This opens the printer properties popup where you can adjust advanced settings.
- Disable dithering via Print Profiles (Advanced tab)
In the printer properties popup, click the Advanced tab and then click Print profiles. Navigate to the Dithering tab and from the dithering type options, select the None checkbox. Click Apply and then OK to save the change.
- Disable dithering via General Preferences
After saving the Print Profiles change, you need to repeat the process for the general settings. Click the General tab in the printer properties window and then click Preferences. Navigate to the Dithering tab again, select the None checkbox, then click Apply and OK.
- Confirm dithering is off and test your labels
Dithering is now disabled for both Print Profiles and General Preferences. Print a Royal Mail label from Zenstores and inspect the 2D barcode — it should appear sharp and clearly defined. Your labels are now ready to produce crisp, scannable barcodes for Royal Mail's delivery confirmation network.
Frequently Asked Questions
Why does my Zebra GK420D produce blurry or unscannable Royal Mail barcodes?
The most common cause is that the dithering setting is not set to None. Dithering applies an image-smoothing algorithm that distorts the fine lines in a 2D barcode, making it difficult or impossible for Royal Mail scanners to read. Disabling dithering in both Print Profiles and General Preferences resolves this.
Do I need to disable dithering in two places?
Yes. The Zebra GK420D has dithering settings in two separate locations: Print Profiles (accessed via the Advanced tab) and General Preferences (accessed via the General tab). Both must be set to None to ensure all labels print correctly, regardless of which print path is used.
Will disabling dithering affect the quality of other labels I print?
For thermal label printing, disabling dithering is generally the recommended setting and will not negatively affect label quality. Thermal printers like the Zebra GK420D are designed to produce sharp output without dithering, so this change improves rather than reduces print quality for barcodes and text.
Does this affect Royal Mail's Online Delivery Confirmation feature?
Yes. Royal Mail's Online Delivery Confirmation relies on the 2D barcode being scanned at each stage of delivery. If the barcode is blurry due to dithering, it may not scan correctly, meaning tracking events will not be recorded. Disabling dithering ensures the barcode is scannable throughout the Royal Mail network.
I've followed the steps but my barcodes still look blurry — what else can I check?
First, confirm you have saved the changes in both Print Profiles and General Preferences by clicking Apply and OK in each popup. Also check that your label stock size is correctly configured in the Zebra driver settings. If the issue persists, try reinstalling the Zebra GK420D driver to reset all settings to their defaults before applying the dithering fix again.
