actor-debugger (Node.js / TypeScript)

Looking for Python Actors? The same one-link browser debugging exists for Python, built on debugpy plus a served DAP frontend — see python/README.md.

Drop-in remote debugging for any Apify Node/TS Actor with a one-line Dockerfile change. It launches your Actor under the Node inspector and serves a full Chrome DevTools UI over the run's container URL — so you open one link in your own browser and debug. No wstunnel, no local setup, no rebuild of your source, and no browser in the Actor.

# Get the package
RUN npm install actor-debugger

# pause on the first line until a debugger attaches (for short-lived Actors):
CMD ["npx", "actor-debugger", "--brk"]

# or point at a specific entry:
CMD ["npx", "actor-debugger", "dist/main.js"]

How it works

1. It resolves your Actor's entrypoint (see detection order below) and launches it as node --inspect=127.0.0.1:9229 <entry> — so the inspector is on your code, in its own process, exactly as it normally runs.
2. It runs one HTTP server on ACTOR_WEB_SERVER_PORT that:
   • serves the Chrome DevTools frontend (static files) so your local browser opens it — no Chrome, Xvfb, or VNC in the Actor;
   • proxies the CDP WebSocket to the inspector, rewriting Host to a loopback IP and dropping Origin. Node's inspector rejects DNS-name hosts (anti-DNS-rebinding), so this rewrite is what lets a browser reach it over <run>.runs.apify.net.
3. The run log prints one URL. Open it in your browser → real DevTools attached to your Actor.

The DevTools frontend comes from chii (MIT), which ships a prebuilt Chrome DevTools frontend. The chrome-devtools-frontend npm package is unbuilt TypeScript source (needs Chromium's GN/ninja toolchain to compile), so it can't be served as-is — chii's build is the same frontend, ready to serve.

Activation

Running the Actor through npx actor-debugger is the switch — debugging is on whenever the CMD line above is in place. To turn it off, revert the CMD to the Actor's normal entrypoint (e.g. CMD ["npm", "start"]) and rebuild. Pass --brk to pause on the first line until a debugger attaches — useful for Actors that would otherwise finish before you connect.

Connect

Open the URL the run log prints, in your own browser:

https://<run>.runs.apify.net/devtools/js_app.html?wss=<run>.runs.apify.net/<uuid>

That page is Chrome DevTools; it connects to your Actor over the container URL. Set breakpoints in your sources (via source maps), step, inspect — no devtools:// URL, no local install. Prefer the raw channel? npx wscat -c "wss://<run>.runs.apify.net/<uuid>", or point Playwright/Puppeteer connectOverCDP at that wss URL.

The WebSocket scheme in the printed URL follows the container URL's scheme: wss on the platform (https container URLs), plain ws on a local Apify dev stack (http on localhost). Always use the URL exactly as printed in the run log.

TypeScript sources (automatic)

A remote DevTools frontend can never fetch file:// URLs from the container, so external .js.map files — the standard "sourceMap": true tsc output — are unreachable to it, and DevTools would fall back to the generated JS ("Source map failed to load"). The debugger fixes this itself at startup: it scans the compiled output, reads each external .map from the container's disk, embeds the original TS text into it (sourcesContent, read from the .ts files in the image), and rewrites the reference into an inline data: URL. Any tsc setup that emits source maps at all (sourceMap or inlineSourceMap) therefore just works — no tsconfig changes needed.

The one unrecoverable case is a build with no source maps: then the run log prints a hint to compile with "sourceMap": true. If the .ts files aren't in the image (a multi-stage build copying only dist/), mappings still inline but sources can't be shown — the log says so; COPY your src/ into the final stage to fix it.

Entrypoint detection order

1. An explicit path argument, if given.
2. The file in package.json scripts.start (e.g. node dist/main.js → dist/main.js).
3. package.json main.
4. Conventional paths: dist/main.js, dist/index.js, build/main.js, src/main.js, main.js, index.js.

Security

The debug endpoint is unauthenticated — anyone who reaches the container URL and the run's uuid can execute code in your run (and read its env, including APIFY_TOKEN). Keep the actor-debugger CMD only in builds you are actively debugging, prefer a restricted run/token, never ship it in a published Actor, and gate the endpoint (owner-only) before any non-prototype use.

Notes

• Depends on chii for the prebuilt DevTools frontend (~16 MB of static assets, no runtime browser).
• Pure Node otherwise — works on any apify/actor-node* base image, no Xvfb / Chrome / apt.