node error listen EADDRINUSE: address already in use after migrating dev server to vite

node error listen EADDRINUSE: address already in use after migrating dev server to vite

TL;DR: Something is already listening on the port (vite defaults to 5173) - almost always the old dev server process still running from before the migration. Find the process on that port and kill it, or point vite at a different port. The error means the port is taken, not that vite is broken.

node error listen EADDRINUSE: address already in use after migrating dev server to vite

Steps

1. Note the port in the error (usually 5173). Find what holds it: lsof -i :5173 on macOS/Linux, or ss -ltnp | grep 5173. Expected: one line showing a node process and its PID listening on the port.

2. Kill it: kill [PID], escalating to kill -9 [PID] if it ignores the first signal. On Windows: netstat -ano | findstr :5173 to find the PID, then taskkill /PID [PID] /F. Expected: re-running the lookup shows nothing listening on the port.

3. Start the vite dev server again (npm run dev or npx vite). Expected: vite prints its Local URL with no EADDRINUSE.

4. If you need both servers up, give vite its own port in the config:

   export default {
     server: { port: 5174 },
   };

   Expected: vite starts on 5174 and both servers coexist.

Use this when

• EADDRINUSE appears the first time you run vite after migrating from webpack-dev-server (or another bundler).
• The port in the error matches the old dev server's port.
• The app worked before the migration and nothing else changed.

Not for this skill when

• EADDRINUSE happens in production or Docker deploys - that is a container port conflict, different fix.
• Vite starts but on an unexpected port (5174, 5175...) - that is vite auto-incrementing because strictPort is off, not an error.
• The address in use is on a remote host, not your machine.

Variant phrasings

• vite dev server port already in use after webpack migration
• Error listen EADDRINUSE 5173 vite
• kill process on port before starting vite

Why it happens

Migrating the config does not kill the old process: the previous dev server (webpack-dev-server, or an earlier vite run in another terminal) is still bound to the port, and the new vite process cannot bind the same one.

Edge cases

• With strictPort off, vite silently moves to the next free port - if your app suddenly lives on 5174, a stale process is the reason.
• A zombie process owned by another user or a hung CI job can hold the port invisibly - check with elevated privileges if lsof shows nothing under your user.
• Terminal tabs and editor-integrated terminals are the usual hiding spots for the forgotten old server.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_JmkIgOvln4jsYgjfT37UcQ