You’re very close — the key is that there are two different “URLs” involved: - What the server binds to (host/port) - What the browser-based UI uses to reach the API Binding the server to

0.0.0.0

is correct, but the UI cannot call

<http://0.0.0.0:4200/api>

from your laptop. You must tell the UI the externally reachable address. In Prefect 3.x, set: -

PREFECT_SERVER_API_HOST

to

0.0.0.0

(bind to all interfaces) -

PREFECT_SERVER_API_PORT

to your port (4200 by default) -

PREFECT_SERVER_UI_API_URL

to the externally reachable URL of your API, e.g.

http://<vm-ip-or-dns>:4200/api

- Optionally, set

PREFECT_API_URL

to the same value for CLI/workers On Windows PowerShell:

$env:PREFECT_SERVER_API_HOST = '0.0.0.0'
$env:PREFECT_SERVER_API_PORT = '4200'
$env:PREFECT_SERVER_UI_API_URL = 'http://<vm-ip-or-dns>:4200/api'
$env:PREFECT_API_URL = 'http://<vm-ip-or-dns>:4200/api'   # optional but recommended
prefect server start --host 0.0.0.0 --port 4200

On cmd.exe:

set PREFECT_SERVER_API_HOST=0.0.0.0
set PREFECT_SERVER_API_PORT=4200
set PREFECT_SERVER_UI_API_URL=http://<vm-ip-or-dns>:4200/api
set PREFECT_API_URL=http://<vm-ip-or-dns>:4200/api
prefect server start --host 0.0.0.0 --port 4200

Quick checks: - From your laptop, open http//<vm ip or dns>4200 - Test the API directly: http//<vm ip or dns>4200/api/hello - Ensure the Windows Firewall (and any network security group) allows inbound TCP 4200 Notes: - If you’re fronting the server with HTTPS or a reverse proxy, set

PREFECT_SERVER_UI_API_URL

to that external HTTPS URL, e.g.

<https://prefect.yourdomain.com/api>

. - Set these env vars before starting the server; the UI reads them at startup. Docs for reference: - Self-hosting Prefect Server - Server CLI options - Windows notes - Settings reference If you share the VM’s IP/DNS and whether you’re using a reverse proxy, I can suggest the exact values to use.

Short answer: yes — as long as the URL you put in

PREFECT_SERVER_UI_API_URL

is reachable from both places. Details: - Set the server to bind on all interfaces:

--host 0.0.0.0

(and open port 4200 in Windows Firewall). - Set

PREFECT_SERVER_UI_API_URL

to a single, consistent URL that both your VM and external clients can reach, e.g.

<http://prefect.yourdomain.com/api>

(or

https://...

behind a reverse proxy). - Then access the UI at the same host/port (e.g., http://prefect.yourdomain.com). If you point

PREFECT_SERVER_UI_API_URL

to a public IP/DNS: - It will work externally. - It will also work from inside the VM if the VM can resolve/reach that public address (hairpin NAT). If not, add a hosts entry or use a DNS name that resolves to the VM’s internal IP on your LAN (split-horizon DNS). If you point it to a private IP: - It will work from inside the network. - It will not work externally. Best practice: use a DNS name (e.g.,

<http://prefect.example.com|prefect.example.com>

) and ensure both internal and external clients (and the VM itself) can resolve it appropriately. Refs: - Server CLI options - Self-hosting Prefect Server