How do I start OAuth Callback Testing on localhost?

Run instatunnel --port 3000 --subdomain oauth-dev, then use https://oauth-dev.instatunnel.my/auth/callback as the public endpoint for this workflow.

What should I verify before calling the workflow done?

Register exact callback URLs and enforce state parameter validation.

High-intent workflow

Test OAuth redirect and callback flows for Google, GitHub, and custom IdPs without repeated staging deploys.

App teams integrating social login and identity provider callbacks.

oauth callback localhost

Command

instatunnel --port 3000 --subdomain oauth-dev

Public endpoint example

https://oauth-dev.instatunnel.my/auth/callback

Public URL	https://oauth-dev.instatunnel.my/auth/callback
Local port	Use the port from your local app command.
Success check	Register exact callback URLs and enforce state parameter validation.

If the provider cannot reach the endpoint, confirm the local app is running and restart the tunnel with the same subdomain.

If events arrive but fail verification, compare the exact public URL and signature secret configured in the provider dashboard.

If retries create duplicates, store the provider event ID before performing side effects.

Free kara hajime, local de kensho, MCP/limits/analytics ga hitsuyo ni nattara upgrade shite kudasai.