A browser cannot talk to a label printer. That is why most tools hand you a PDF and a print dialog, which is fine once and unbearable forty times in an evening. A small helper application on the computer with the printer closes that gap, it works with whatever printer that computer already has, and everything above it is built so that you never think about it again.
No download, no dialog, no choosing the printer each time, no dragging files between the show and the packing table. The job arrives and the printer runs. During a show this is the difference between automation and a second job.
You install it once on the computer your printer is attached to. It talks to your browser over a secure connection that never leaves that machine. It only needs to run on the computers that actually print, which is not necessarily the one you host from.
The label goes to whatever is installed on that machine: the 4x6 thermal unit at the packing table, the office laser, the all-in-one in the spare room. There is no supported-model list to check against and no particular brand to go out and buy, because what we hand the printer is a finished page rather than a set of instructions only one make of hardware understands. If you already own a printer, it already works.
The helper reads the list of printers installed on that computer and you pick one by name. You do not type a queue name, copy a driver string, or find out which of four similar names is the right one by printing to each in turn.
Printing from a page you do not own is genuinely hard, and doing it properly meant routing the handshake back through our own domain so the helper will accept the connection. The result is that your printer works on the Whatnot tab where you actually spend the show, not only inside our app.
A colour-coded indicator sits in the header at all times, and it separates states that need different fixes: helper not installed, helper running but no printer set up yet, printer set up on another computer, and cannot reach us from this page. Four problems, four messages, instead of one red dot.
The connection is re-probed on a timer and again whenever the app reconnects, so starting the helper mid-show is noticed on its own. You do not reload anything to make the indicator go green.
If the helper is not there, the panel says so in plain language and offers the download and the steps, rather than reporting a connection error and leaving you to work out what it wanted from you.
The settings page states in words which computer and which printer each kind of label is going to, so the answer to "where is that coming out" does not require reading a table.