Hardware harness
The hardware harness is a set of small browser apps — one per printer family — that check a real printer against its driver. Each one pairs the printer over WebUSB or Web Bluetooth, runs an identity probe and a single diagnostic print, and hands you a pre-filled verification report. No install, no SDK, no command line — it runs in a browser tab.
Open a harness
| Printer family | Harness | Connects over |
|---|---|---|
| Brother QL / PT | Brother QL harness | USB (WebUSB) |
| DYMO LabelManager | LabelManager harness | USB (WebUSB) |
| DYMO LabelWriter | LabelWriter harness | USB (WebUSB) |
| DYMO LetraTag | LetraTag harness | Bluetooth (Web Bluetooth) |
| Marklife / Deli / AbleMark | Marklife harness | Bluetooth (Web Bluetooth), USB (WebUSB), Serial (Web Serial) |
Each harness needs a Chromium-class browser — Chrome, Edge, or similar. WebUSB and Web Bluetooth are not available in Firefox or Safari.
Why it exists
Every row in the compatibility matrix is a claim, and a claim is only as good as the evidence behind it. The maintainer can't own every printer — most cells start as Likely works, inferred from a verified sibling rather than directly tested.
The harness closes that gap. Anyone with the hardware can run it and file a report, which turns a Likely works cell into Verified for everyone who buys the same model. It is the shortest path from "I have this printer" to a data point the next person can trust.
How to use it
- Open the harness for your printer family from the table above.
- Connect the printer, click Pair, and pick it from the browser's device chooser.
- Run the identity probe — it confirms the harness is talking to the model you expect.
- Run the diagnostic print — one small label that exercises the driver's encoder end to end.
- Submit the report — the harness opens a pre-filled GitHub issue on the driver repo with the device, the result, and room for your notes. Review it and file.
The flow is observation-only: one diagnostic label out, status back. It never touches firmware or printer settings.
Printer won't connect?
WebUSB and Web Bluetooth can only reach a printer the operating system has handed to the browser. On Windows that usually means installing a WinUSB driver with Zadig; on Linux it means a udev rule. Both are walked through on the connecting your printer page.