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Zebra label printers such as the ZD421d, ZD420d, ZD220, and GK420d need to be configured with the correct paper size before printing shipping labels. The paper size should be set to 102x192mm or 100x150mm depending on the labels you are using.

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Paper size on your computer

The Zebra label printers are installed on Mac like any other printer. Make sure to select the Zebra ZPL Label Printer driver.To configure the paper size:
  1. Open a test label in the Preview app
  2. Select Print
  3. Under Paper Size, select “Manage Custom Sizes…”
  4. Press + to add a new size
  5. Specify the custom paper size:
    • Width: 102mm
    • Height: 192mm
    • Non-Printable Area: User defined
    • Top: 0 mm, Right: 0 mm, Bottom: 0 mm, Left: 0 mm
  6. Double-click the paper size to rename it to “102x192mm”
Once configured, select that printer when printing shipping labels.

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Printer models

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Zebra GK420d

If the green status light flashes and nothing prints, the printer is probably paused. Press Feed once. The light should turn solid green, and the printer resumes printing.
The GK420d has no display. Everything you can set from the printer runs through the Feed button and the green status LED.With the printer switched on and the top cover closed, press and hold Feed. The green LED flashes in sequences — one flash, then two, then three, and so on. Release the button after the sequence you want and before the next one starts.
Releasing after the second flash runs a standard auto media calibration. The printer detects the type and length of the labels you have loaded and adjusts its media sensors to match, feeding one to four labels while it works.Run it when you load a different label stock, or when the printer skips labels, prints across the gap between labels, or feeds blank labels.If auto calibration does not get it right, keep holding to the seventh flash instead. That runs a manual media calibration , a more extensive set of tests for stock the automatic routine cannot read.
Releasing after the first flash prints the configuration status label — the printer’s current settings, including darkness, print speed and label size. Print one before you change any setting so you have a record of where you started, and again afterwards to confirm the change stuck.On a GK420d with the internal print server option, the lower half of this label also lists network settings such as the IP address, which is the quickest way to find the address of a printer you cannot reach. Networked models print an additional network configuration label as well.
Releasing after the sixth flash prints a succession of barcode patterns at increasing darkness levels. Press Feed once when the pattern is clear and legible, and the printer keeps that darkness.This is the on-printer alternative to the Print Quality Assistant when you have no computer or phone to hand.
For the full list of sequences, see Zebra’s Feed button modes .
Holding Feed while you switch the printer on is a different mode and enters firmware download. Power the printer up first, then hold Feed.

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Zebra ZD420d and ZD421d

If the PAUSE indicator is lit, the printer is paused. Press the PAUSE button once to resume printing.
These models use button combinations rather than flash counts. Wait until the printer is ready — the STATUS indicator lit solid green — before pressing anything.
With labels loaded and the top cover closed, press and hold PAUSE and CANCEL together for two seconds, then release. This is SmartCal media calibration: the printer feeds and measures several labels and adjusts its media sensing levels. The STATUS indicator returns to solid green when it succeeds.Run it when you load a different label stock. You do not need to repeat it for another roll of the same stock — a press or two of FEED is enough to resynchronise the printer.See Zebra’s instructions for the ZD421 and ZD621 or the ZD420 and ZD620 .
Press and hold FEED and CANCEL together for two seconds, then release. The printer prints both the printer configuration report and the network configuration report, then returns to ready.The network report covers the Ethernet, Wi-Fi and Bluetooth settings, so this is the quickest way to read the IP address of a printer you cannot reach from your computer. The printer report gives you the current darkness, speed and label size.See Zebra’s instructions for the ZD421 and ZD621 or the ZD420 and ZD620 .
The print quality report prints a range of test labels at speeds and darkness levels above and below the printer’s current settings, so you can pick the best one by eye.
  1. Print a configuration report with FEED + CANCEL so you know the current darkness value.
  2. Switch the printer off.
  3. Press and hold FEED while you switch the printer on. Release FEED when the status indicator is the only indicator lit.
  4. Find the label that prints best. Bars and spaces should be distinct and the text complete — not so dark that small text fills in, and not so light that the bars lose definition.
  5. Add the relative darkness value printed on that label to your current darkness value, and set the result on the printer.
See printing a print quality report .
Calibrating the label size on the printer is not the same as setting the paper size on your computer. Both need to match your labels, so work through Paper size on your computer above as well.