yt-thermal-printer

Prints a YouTube "now watching" receipt to an XP-80 thermal printer every time the playing video changes inside a playlist.

How it works

   ┌────────────────────────────┐        POST /print          ┌───────────────────────┐
   │  Chrome / Edge extension   │   ───────────────────────▶  │  yt_printer.py        │
   │  (content script in       │   { title, channel,         │  local HTTP server    │
   │   youtube.com tab)         │     playlist, elapsed,      │  127.0.0.1:7878       │
   └────────────────────────────┘     duration, thumbnail }   └──────────┬────────────┘
                                                                          │ ESC/POS raster
                                                                          ▼
                                                                ┌───────────────────┐
                                                                │  XP-80 (USB)      │
                                                                │  Windows spooler  │
                                                                │  driver: Generic  │
                                                                │  / Text Only      │
                                                                └───────────────────┘

• The content script watches youtube.com/watch?v=…&list=… pages. When the v= parameter changes, it waits ~1.5 s for metadata to settle, then POSTs the current track to the local server.
• The server is a tiny http.server-based Python app. It downloads the video thumbnail, renders a 576-pixel-wide receipt image with PIL (YouTube logo, title, channel, playlist, progress bar, playback controls), packs the bitmap into an ESC/POS GS v 0 raster command, and writes it to the XP80 Windows print queue via the Win32 spooler API (win32print).
• No Xprinter driver is required — the printer is bound to Windows' built-in Generic / Text Only driver on port USB002. That driver passes raw bytes straight through to the device.

Requirements

• Windows (the server uses win32print)
• Python 3.10+
• An Xprinter XP-80 (or any ESC/POS-compatible 80 mm thermal printer) visible to Windows on a USB port
• Chrome, Edge, or another Chromium-based browser

One-time setup

1. Bind the printer to a Windows print queue

If Get-Printer doesn't show your XP-80, run this in PowerShell as administrator (replace USB002 with whichever port your device enumerated on):

Add-PrinterDriver -Name "Generic / Text Only"
Add-Printer      -Name "XP80" -DriverName "Generic / Text Only" -PortName "USB002"

You can find the right port in Device Manager → the "Printer POS-80" entry → Properties → Details → "Bus relations" (or just look for USB00n in the PowerShell output of Get-PnpDevice -Class USBPrint).

2. Install Python dependencies

pip install pywin32 Pillow

3. Load the browser extension

1. Open chrome://extensions
2. Enable Developer mode (top-right)
3. Load unpacked → pick the yt_extension/ folder
4. (Optional) Pin the extension; click its icon for endpoint settings, a "Ping server" button, and a "Test print" button.

The first time the content script POSTs to 127.0.0.1, Chrome will pop up a Private Network Access prompt — accept it. After that the request goes through silently.

Running

:: terminal stays open while serving — close it to stop
start_server.bat

…or run it manually:

python yt_printer.py --serve

Then play a video inside a playlist on YouTube. Every time the track changes, a receipt comes out of the printer.

CLI options

yt_printer.py is dual-purpose: it can run as a server, print a one-off mock receipt, or save a PNG preview for layout iteration without burning paper.

Flag	What it does
--serve	Start the HTTP print server (default port 7878)
--host	Bind host (default 127.0.0.1)
--port	Bind port (default 7878)
--printer	Windows print queue name (default XP80)
--preview	Save preview_yt.png instead of printing
--title etc.	Override mock-data fields when printing one-off

Example — preview a layout without printing:

python yt_printer.py --preview --title "Some Track" --channel "Some Channel"

HTTP API

POST /print accepts JSON:

{
  "title":     "Video title",
  "channel":   "Channel name",
  "playlist":  "Playlist name",
  "elapsed":   "0:42",
  "duration":  "3:33",
  "thumbnail": "https://i.ytimg.com/vi/<id>/hqdefault.jpg"
}

All fields are optional except title. elapsed / duration use m:ss format. GET /health returns a small JSON OK for liveness checks.

Extension settings

Click the extension's toolbar icon to:

• toggle the printer on/off,
• change the server endpoint (e.g. another machine on the LAN),
• manually fire a "Test print" with mock data,
• "Ping" the server for a quick liveness check.

By default the content script only prints when the URL contains a list= parameter (so single-video pages won't spam the printer). To print on every video, change REQUIRE_PLAYLIST to false in yt_extension/content.js.

Files

yt-thermal-printer/
├─ yt_printer.py           server + ESC/POS raster generator
├─ start_server.bat        one-click server launcher (Windows)
├─ yt_extension/
│  ├─ manifest.json        MV3 manifest
│  ├─ content.js           DOM watcher + POST to /print
│  ├─ popup.html           settings UI
│  └─ popup.js
└─ .gitignore

Notes / limitations

• The thumbnail is dithered to 1-bit with Floyd-Steinberg. High-contrast images print clearly; busy thumbnails turn into a haze.
• The print head and cutter have a physical offset; the server feeds 6 line-feeds after the image before cutting so nothing gets sliced through. If your model's cutter is further away, increase BOTTOM_PAD in yt_printer.py.
• The XP-80's printable width is 576 px (72 mm at 8 dots/mm). Don't change WIDTH unless you have a different printer.
• The extension targets the current YouTube watch-page DOM. YouTube changes selectors occasionally; if titles or channel names stop showing up, update the selector lists in gather() inside content.js.

License

MIT.