The print bridge: what it is and why you need it

Laberty lives on the internet. Your printers live on your home or shop network. Nothing on the internet can reach them, and that's how it should be. The print bridge is how the two meet.

How it works

Laberty (cloud)  <── HTTPS, outbound only ──  bridge (your network)  ── port 9100 / CUPS ──>  printers

Something in Laberty creates a print job: you, a birthday occasion, or one of your own apps. The job waits in a queue.
The bridge asks Laberty for work every 5 seconds.
It picks up the job. The job carries the printer's address, so the bridge knows where to send it.
It sends the job to the printer and reports back whether it printed. If it didn't, the job records why.

The bridge only ever makes outbound connections. There are no ports to open, no port forwarding and no VPN.

Do I need it?

You want to…	Bridge needed?
Print address labels or notes from an iPhone or iPad, through the Share menu	No
Have Print go straight to the printer, with no print dialog	Yes
Print to a receipt printer (ESC/POS)	Yes
Print to a Zebra or other ZPL printer	Yes
Print to a Brother QL by its IP address	Yes
Print to a USB printer plugged into a Windows PC	Yes, Laberty Bridge for Windows
Have occasion labels print themselves, with nobody tapping anything	Yes
Send appointment cards straight to the printer ("To agent")	Yes
Let your own app print through Laberty	Yes

The bridge comes with Home and Business. The Free plan prints from a phone or tablet only.

One bridge, every printer

You don't set printers up on the bridge. You type each printer's IP address into Laberty, on Admin → Printers & stock, and every job carries that address. Adding a printer is a web form, not a config file and a restart.

Every Print goes straight to the printer

Once the bridge is connected, pressing Print anywhere in Laberty prints, with no print dialog. That covers the member's address labels and notes, Ask Laberty, food labels, appointment cards and calendar strips, and the admin Printing page. Nothing needs switching on.

It sends the exact same PDF the print dialog would have had, to the default printer.
The person sees Sending your labels to the printer…, then Printed ✓.
If the job fails, or the bridge hasn't picked it up within about 45 seconds, they get one button. On the member's screens it's Print from this iPad instead. On admin screens it's Open the PDF instead. A job the bridge never picked up is taken off the queue then, so it can't print twice later.
If the bridge hasn't been seen for a few minutes, Print opens the print dialog (or the PDF) straight away, as it did before.
It needs Home or Business, and a default printer with an IP address, or a queue name for a driver printer.
To always use the print dialog instead, tick Always use the iPad or phone print dialog instead in the When someone presses Print box on Admin → Printers & stock. The same box lists recent prints through the bridge, and Admin → Print bridge says where prints go right now.
The appointments page's To agent button and occasion auto-print work as before.

More in Printing from an iPhone or iPad.

The bridge asks the printer what's in it

A job made for the wrong roll doesn't just come out wrong. A Brother QL stops, puts its light on, and stays that way until somebody walks over and presses the button on it. If the printer lives in someone else's house, that's a phone call and a drive.

So before it sends anything, the bridge asks the printer what is physically loaded. It tries three ways, in order, and stops at the first real answer:

IPP (the same thing AirPrint uses), which is what a QL-820NWB should answer.
SNMP, the standard way printers report their paper tray.
Brother's own status request, last, because some QL firmware ignores it over the network.

What happens then:

The right roll is in it. It prints, exactly as before.
The wrong roll is in it. Nothing is sent. The printer is left alone, so it never goes into an error state and never needs the button. The job waits under Ready to print on Admin → Print bridge as "needs the Large Address roll", and your admins get one email. Put the right roll in and press Print.
The printer doesn't answer. Everything works exactly as it did before this existed — the job is sent, and the printer's own errors are reported.

Each question has a two-and-a-half second limit and the answer is remembered for 30 seconds, so a batch of labels asks once. Nothing here can stop you printing: only a real answer from the printer can hold a job back.

When the printer does answer, Laberty believes it over its own record: if what the printer describes is one of your label sizes, that becomes the roll it has in, marked Confirmed. If it's a size you don't have, Laberty shows what the printer said on the printer's card and changes nothing.

Ask right now. Each printer's card on Admin → Printers & stock has Ask the printer what's loaded. The answer appears within a few seconds, with which of the three ways answered and exactly what the printer said.

If the printer is already showing an error

The bridge tries one safe reset (nothing prints, nothing feeds) and asks again. If the printer is still unhappy, the job stops with the reason and the printer's card says: the printer is showing an error — press the button on the printer, then press Retry.

Brother printers sometimes still need that button. Once a QL has gone into an error state — usually from a job sent before you had this, or from a phone app — the reset clears most cases but not all. Some faults only clear at the printer.

"Is the Large Address roll in the printer?"

Some printers never answer any of the three questions above. For those, there's one more safeguard: when Laberty isn't sure which roll is in, whoever presses Print is asked, once, before anything is sent:

Is the Large Address roll in the printer? Yes, print · or the other rolls to choose from

They're standing next to the printer, so they can see. Yes confirms it and prints. Picking a different roll confirms that one instead, and prints if the labels fit it — otherwise it's the "different roll is in the printer" screen, with the same button to print from the iPad.

You only see this question when Laberty doesn't know:

If the printer reported what it has in the last few minutes, there's no question.
If the roll is already confirmed, there's no question.
Otherwise it's asked again once the confirmation gets old. That's Ask again after in the Who can confirm a roll "for sure" box on Admin → Printers & stock — 24 hours by default, and 0 means never.
A person's answer stops blocking after 12 hours, whatever that setting says. A roll someone confirmed by answering the question (or through Admin or the API) can be swapped without telling Laberty, so after 12 hours Laberty stops refusing prints against it and the printer's own error is the check again. A roll confirmed by a Laberty device, or reported by the printer itself, doesn't expire this way.

Laberty Screens, switches and apps are never asked: a switch or a confirm button already says which roll is in, and apps get a clear refusal instead.

When the roll is confirmed

Each printer's roll is either Confirmed or Not sure, on its card on Admin → Printers & stock.

Not sure (the default): every print goes to the printer. If it's the wrong roll, the printer says so (a Brother QL that answers its status check), the job fails, and the person gets Print from this iPad instead.
Confirmed: Laberty already knows which roll is in, so a print made for another roll never goes to the printer. Nothing is queued. The member sees "The printer has the Large Address roll in it. Change the roll, then tap Swap roll in Laberty — or print from this iPad." on the same page as the print button. If a switch confirmed the roll, it says "Change the roll and flip the switch" instead, and if a confirm button did, "Change the roll and press Confirm on the device".

A roll is confirmed from a Laberty device at the printer: a roll switch, or a confirm button. Admin and apps can confirm it too if an admin allows them. See Label stock: Confirmed or Not sure.

A job that was already waiting when the roll changed is checked again when the bridge picks it up. Occasion labels go back to Ready to print. Anything else fails with stock_mismatch, and your admins are emailed. The bridge moves straight on to the next job.

If a confirmed roll turns out to be wrong (the printer reports different labels), Laberty goes back to Not sure and emails your admins. More in Label stock: Confirmed or Not sure.

What it runs on

Any computer that stays on and shares a network with your printers: a desktop, a mini PC, a Raspberry Pi, or a NAS. You download it from Admin → Print bridge: a Docker package that builds itself on your machine, or on a Windows PC, a small program that starts with Windows.

Laberty Bridge for Windows: for printers plugged into a Windows PC by USB, or any printer that PC prints to. No Docker.
Installing the bridge with Docker (Windows, Mac and Linux)
Installing the bridge on a Synology NAS

Run one bridge per Laberty account.

The bridge key

The bridge signs in with a bridge key. It's an API key that can only pick up print jobs and report them done. It can't read your households or send jobs of its own.

Admin → Print bridge → Download your bridge makes one for you and puts it inside the download, so there's nothing to copy. Every download makes a new key, named like Bridge download 2026-09-26 (Windows).
Keep the ZIP to yourself: anyone with the key can pick up your print jobs. Delete it once the bridge is running.
It never expires. To switch a bridge off for good, revoke its key on Admin → API keys.

Is it running?

Admin → Print bridge shows "● Bridge is running" when the bridge picked up a job in the last five minutes.
"○ Not seen recently" can simply mean it has had nothing to print. A quiet bridge is still healthy. Press Send a test page to the print agent on Printers & stock to be sure.
On the bridge machine, docker logs laberty-bridge shows what it's doing. connected to https://laberty.app — waiting for print jobs means all is well.

If jobs are waiting and nothing prints, work through Nothing printed.

A screen by the printer

A Laberty Screen shows the bridge and printer at a glance: the roll loaded, jobs, labels waiting to print and upcoming occasions. It can be a small touchscreen, a knob, an e-ink sign, or an old tablet. See Laberty Screen.

Security notes

The bridge runs as a non-root user and stores nothing.
It connects only to Laberty and to the printer addresses Laberty gives it.
It will print to any address set in Laberty, so only give admin accounts to people you trust with your network.