Replit Playwright Chromium

Playwright (Chromium) on Replit — no download

Replit ships a Playwright-managed Chromium in the Nix store, exposed as $REPLIT_PLAYWRIGHT_CHROMIUM_EXECUTABLE. playwright install (which only downloads a browser) is both unnecessary and broken here — point Playwright at the store browser with executable_path and be done.

If you need Firefox-level anti-detection instead of Chromium, use the camofox-on-replit skill. Replit platform gotchas ($HOME wipes, XDG persistence, registry firewall) live in the replit-knowledge skill; Nix/closure mechanics live in replit-nix.

The 4 steps

# 1. The browser is already there — verify it runs:
export CHROME="$REPLIT_PLAYWRIGHT_CHROMIUM_EXECUTABLE"
"$CHROME" --headless=new --no-sandbox --disable-gpu \
  --dump-dom https://example.com 2>/dev/null | grep -o "<title>.*</title>"
# -> <title>Example Domain</title>   (dbus/gcm/GLib stderr noise is harmless)

# 2. Install ONLY the Python package (never `playwright install`):
pip install playwright          # pip missing? python3 -m venv .venv && .venv/bin/pip install playwright

# 3. Launch it (standalone script):
python - <<'EOF'
import asyncio, os
from playwright.async_api import async_playwright

async def main():
    async with async_playwright() as p:
        b = await p.chromium.launch(
            executable_path=os.environ["REPLIT_PLAYWRIGHT_CHROMIUM_EXECUTABLE"],
            headless=True,
            args=["--no-sandbox", "--disable-gpu", "--disable-dev-shm-usage"],
        )
        page = await b.new_page()
        await page.goto("https://example.com")
        print("title:", await page.title())
        await b.close()

asyncio.run(main())
EOF

# 4. (agent/CDP use) daemon it on :9222 for any CDP client:
"$CHROME" --headless=new --no-sandbox --disable-gpu \
  --remote-debugging-port=9222 \
  --user-data-dir="${XDG_DATA_HOME:-$HOME/.local/share}/chromium/default" about:blank &
curl -s http://127.0.0.1:9222/json/version   # -> "Browser":"Chrome/..." + ws URL

--no-sandbox is required (no usable setuid sandbox in the container). executable_path must be the expanded absolute path (env var, not $VAR string). The store chrome is a ~438-byte launcher script, not an ELF — normal, run it as-is.

CDP daemon: on-demand, not always-on

Run the :9222 daemon only while you need it; kill it when the task is done. Do NOT schedule it on cron — the container dies and nothing restarts it. scripts/ensure_browser.sh is the idempotent launcher (no-op if the port is already live); it drives the store browser only — there is deliberately no fallback to any other browser on PATH.

Where Chromium keeps data. The store launcher does not set a profile dir, so an unmanaged launch uses Chromium's default: $XDG_CONFIG_HOME/chromium — on Replit that's pre-set to $REPL_HOME/.config/chromium, i.e. workspace (persists; $HOME is wiped on recreate). ensure_browser.sh passes an explicit --user-data-dir instead: $CHROME_DATA_DIR (default $XDG_DATA_HOME/chromium/default).

Multiple agents sharing one sandbox. Chromium locks --user-data-dir (SingletonLock) — two instances can NEVER share one profile dir; the second either fails or refuses the lock. Never share; run one daemon per agent with its own port and data dir:

CHROME_PORT=9223 CHROME_DATA_DIR="$XDG_DATA_HOME/chromium/agent-b" \
    bash scripts/ensure_browser.sh

Pitfalls

• Never playwright install on Replit — it only downloads (and fails under the registry firewall). The browser is in the Nix store.
• Registry firewall: plain pip install uses the pinned PyPI index; if a mirror 404s, export PIP_INDEX_URL=https://pypi.org/simple/. (npm equivalent: see replit-knowledge.)
• LD_LIBRARY_PATH: usually unnecessary — the Nix chrome wrapper points at its own store. Only touch it if you see cannot open shared object file, and then use the closure method from replit-nix §3, never a hand-picked partial list.
• Playwright scripts and CDP are independent lanes to the same browser; neither needs agent-browser or any other npm driver.

Verification

• Step 1 prints the Example Domain title (store browser launches).
• Step 3 prints a real page.title() (Playwright→store-browser wiring).
• Step 4: /json/version returns a ws URL and any CDP client loads a page.

Files in this skill

• scripts/ensure_browser.sh — idempotent, on-demand CDP daemon launcher (source of truth for the :9222 launch line; per-agent CHROME_PORT / CHROME_DATA_DIR overrides).
• scripts/monitor.sh, scripts/browser_monitor.py — the opt-in :5000 screenshot relay (monitor.sh on → https://$REPLIT_DOMAINS:5000, off by default).