/APIs & SDKs/Configuration commands/dev

Neon CLI command: dev

Run Neon Functions locally with a dev server

The dev command runs Neon Functions locally with a dev server and hot reload. Serve one function from its entry module, or every function declared in your neon.ts policy.

Usage

neon dev [--source <path>] [options]

Options

Option	Description	Type	Default	Required
`--port`	Port to listen on (single-function mode only, with --source). Fails if taken. Without it (and without a PORT env var) a free port is chosen automatically.	number	—	No
`--source`	Path to a single function entry module. Omit to serve every function declared in neon.ts.	string	—	No

Examples

Serve one function on a free port with hot reload:

neon dev --source ./functions/hello.ts

Serve every function declared in neon.ts (one dev server each):

neon dev

Serve one function on an explicit port (fails if the port is taken):

neon dev --source ./functions/hello.ts --port 3000

WebSockets

neon dev serves WebSocket upgrades locally, so you can test real-time functions before you deploy. Connect a client to the dev server's ws://localhost:<port> URL. See WebSockets and SSE for the function-side code.

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