ERR_NGROK_4018: ngrok authentication failed

ERRNGROK4018: ngrok authentication failed

TL;DR: ngrok has no idea who you are. Grab your authtoken from the ngrok dashboard and run ngrok config add-authtoken [your token]. If it still 4018s after that, your account email is not verified — verify it, then retry.

ERROR:  authentication failed: Usage of ngrok requires a verified account and authtoken.

ERROR:  Sign up for an account: https://dashboard.ngrok.com/signup
ERROR:  Install your authtoken from https://dashboard.ngrok.com/get-started/your-authtoken

ERROR:  ERR_NGROK_4018

Steps

1. Find your authtoken at the top of the ngrok dashboard setup page.

1. Install it:

ngrok config add-authtoken [your authtoken]

Expected: Authtoken saved to configuration file: [path]/ngrok.yml.

1. Start the tunnel:

ngrok http 3000

Expected: the session panel shows account with your email and no 4018.

1. Headless or CI alternative: set NGROK_AUTHTOKEN in the environment instead of writing the config file — ngrok picks it up natively.

When this applies

• the exact 4018 error on startup
• first run on a new machine, or CI where the config file wasnt carried over
• authtoken rotated in the dashboard and the saved one is stale

When it doesnt

• ERR_NGROK_322 — the free tier allows one simultaneous session; stop the other one
• tunnels that start then die — that is the app behind the tunnel, not auth

Compatibility

ngrok v2 and v3 CLI.

Why it happens

ngrok ended anonymous tunnels: every agent session must present an authtoken bound to a verified account. The CLI reads it from ngrok.yml or the NGROK_AUTHTOKEN env var — if both are absent, wrong, or the account is unverified, the edge rejects the session with 4018.

Edge cases

• config file location differs per OS (~/.config/ngrok/ngrok.yml on Linux)
• rotating the token in the dashboard invalidates the saved one — re-run add-authtoken afterwards
• in Docker, bake NGROK_AUTHTOKEN into the container env, not into the image

Find this skill again

curl -s 'https://vectle.com/api/v1/search?q=ngrok+ERR_NGROK_4018+authentication+failed'