Print labels on a Phomemo D30 from a browser tab, over Bluetooth. No app, no account, nothing to install.

codebutler.github.io/labelprinter

Build a list of labels and press Print once to send the whole batch. Each label has its own quantity, and text uses any of the ~1,900 Google Fonts.

A Chromium browser — Chrome, Edge, Arc, Brave — on desktop or Android. It needs Web Bluetooth, which Safari and Firefox don't implement, so iOS is out entirely. The page must be served over HTTPS or from localhost.

Press Connect and pick the printer. The connection stays open, so the header shows the device's own name and the readout tracks battery, paper and cover while you work — open the cover and it says so within a few seconds.

Type straight onto any label preview; each preview also has its own quantity control. What's on screen comes from the same drawing code as the canvas sent to the printer.

• Text size — Auto chooses the largest size that fits every label, so the whole batch uses consistent type. Fixed sets a ceiling and still shrinks the batch to fit under it.
• Label size — the stock in the printer. 12 × 40 mm and 14 × 60 mm are presets; Custom takes any dimensions.
• Debug — a hex log of everything sent and received, decoded; a density control; and calibration nudges for a printer that lays the image down off-centre.

Printing is confirmed rather than assumed: the status reads Printed only when the printer says so. If it reports nothing back, you get Sent — not confirmed instead, because bytes leaving the browser aren't ink on tape.

The printer takes a 1-bit raster, one row at a time, over a GATT characteristic on service 0xff00. At 203 dpi that's 8 dots/mm, so a 12 × 40 mm label is exactly 96 × 320 dots.

Text is drawn to a canvas rotated 90°, since the tape feeds sideways relative to the head. Two canvases are kept: a high-resolution one for the preview, and one at the printer's own resolution that becomes the payload. Both come from the same drawing code.

Two things worth knowing if you're changing this:

• The print head is 96 dots wide regardless of the tape. 12 mm is all it can reach; wider stock just gets a 12 mm band. Sending wider rows makes the printer drop the job silently.
• Canvas falls back to a default face when a font hasn't loaded, without telling you. Every measure/fit/draw waits on document.fonts.check first, or the label gets sized against the wrong font.

The command set and status responses were read off the decompiled vendor Android app and are documented in src/protocol.ts: commands are 1f 11 xx, replies are a type byte plus payload — 0f 0c for print complete, 05 99 for cover open, and so on.

bun install
bun run dev

Then bun run lint and bun run build — the same two the deploy runs.

The font catalogue is generated, not hand-written. bun run fonts:generate rebuilds src/google-fonts.json from the google-font-metadata package: every family with a latin subset, with the weights it actually ships. It's checked in, so a build never needs the network.

React 19, Vite, Tailwind v4, and shadcn components on Base UI.

Pushing to main publishes to GitHub Pages via .github/workflows/deploy.yml. Lint and build run first, so a type error fails the deploy instead of shipping a broken page.

Hosting it elsewhere means changing base in vite.config.ts — it's set to /labelprinter/ for the project-site subpath, and wants to be / at a domain root.

MIT