How to use Playwright with Nullprint

What it is

Playwright is Microsoft's open-source browser automation library. Nullprint starts the profile; Playwright attaches to it over the Chrome DevTools Protocol.

Set it up in Nullprint

1. Keep the Nullprint app running. Find the port and key in ~/.nullprint/daemon.json (Windows: %USERPROFILE%\.nullprint\daemon.json). The key is also on the Automation page.
2. Turn on External debugging for the profile: open the profile, expand Expert mode and tick External debugging (it asks for step-up verification). From a script, do the same two things: POST /profiles/{name}/external-debug-grant with an x-np-stepup ticket, then PATCH /profiles/{name} with {"launch": {"externalDebug": true}}. Without both, cdp_endpoint stays null — profiles don't open a debugging port by default.
3. Install: pip install requests playwright
4. Launch the profile, wait for its CDP endpoint, attach:

   import json, os, time, requests
   from playwright.sync_api import sync_playwright
   
   cfg = json.load(open(os.path.expanduser("~/.nullprint/daemon.json")))
   BASE = f"http://127.0.0.1:{cfg['port']}"
   H = {"X-API-Key": cfg["api_key"]}
   NAME = "shop-01"  # the internal ID from GET /profiles, not the display label
   
   requests.post(f"{BASE}/profiles/{NAME}/launch", json={"headless": False}, headers=H).raise_for_status()
   while True:  # launch is asynchronous
       p = requests.get(f"{BASE}/profiles/{NAME}", headers=H).json()
       if p.get("status") == "running" and p.get("cdp_endpoint"):
           break
       time.sleep(1)
   
   with sync_playwright() as pw:
       browser = pw.chromium.connect_over_cdp(p["cdp_endpoint"])
       ctx = browser.contexts[0]
       page = ctx.pages[0] if ctx.pages else ctx.new_page()
       page.goto("https://example.com")
       print(page.title())
       browser.close()  # only disconnects
   
   requests.post(f"{BASE}/profiles/{NAME}/stop", headers=H)  # this closes the browser

5. Node.js: same steps with chromium.connectOverCDP(endpoint).

Full API reference: Local API docs

Why they work well together

• Your script runs inside a real, persistent profile, so cookies, fingerprint and proxy stay the same between runs.
• Time zone, language and geolocation already follow the profile's proxy; the script doesn't have to fake them.
• Need a fixed port for a long-running job? Set launch.debugPort on the profile.