localhost:8787: what runs on it and how to open it
Port 8787 is the default for the Cloudflare Wrangler dev server. How to open it and fix errors.
Open this address: http://localhost:8787This opens on your own computer. It only works if the program is running.
localhost:8787 is where Wrangler serves your Cloudflare Worker while you develop. It runs while wrangler dev stays open in a terminal.
What runs on localhost:8787
- Cloudflare Workers with
npx wrangler dev
Commands to start and test port 8787
npx wrangler devnpx wrangler dev --port 8788Find what is using port 8787
Run these in a terminal on your computer. Nothing is sent to this site.
If localhost:8787 will not open
- Port 8787 is already in use
- Another program is on port 8787. Find it with the tool below and stop it, or start yours on another port.
- This site can’t be reached (ERR_CONNECTION_REFUSED)
- The server is not running. Start it and keep that terminal open. See the full checklist.
- Works on your computer, not on your phone
- Start the server on all network addresses and use your computer’s IP address. See how to open localhost from your phone.
Other ports like 8787
| Port | Usually used by |
|---|---|
| localhost:3000 | React, Next.js, Express |
| localhost:5173 | Vite dev server |
| localhost:4200 | Angular dev server |
| localhost:5000 | Flask |
| localhost:8000 | Django, PHP, Python |
| localhost:8080 | Tomcat, Spring Boot, Docker |
| localhost:8888 | Jupyter Notebook |
Questions about localhost:8787
- What runs on localhost:8787?
- The local development server of Cloudflare Wrangler.
- Is localhost:8787 safe?
- Yes, as long as it stays on localhost. Only your own computer can reach localhost:8787. It becomes reachable from other devices only if you start the program on 0.0.0.0 or your computer's IP address. Development servers are for testing, so do not put them on the public internet.
- Can I use a different port instead of 8787?
- Yes. Most programs let you choose the port with a setting or a command option. Pick a free port above 1024 and open that number instead, for example localhost:8788.
- How do I check what is using port 8787?
- Use the port checker on this page. It shows the command for Windows, macOS and Linux and does not send anything to this site.
- Can I open localhost:8787 from my phone?
- Yes, if both are on the same Wi-Fi. Start the program so it listens on all addresses, then open your computer's IP address with :8787 on the phone. A firewall on the computer can still block it.
Free tools that help
- Common ports listSearch a list of common TCP and UDP port numbers: SSH 22, HTTP 80, HTTPS 443, MySQL 3306, PostgreSQL 5432 and more, with dev server ports.