Why is my website down? A troubleshooting checklist

1. Define what “down” means

Record the exact error, affected URL, time, and whether the problem appears on multiple networks or devices. A browser timeout, DNS error, certificate warning, HTTP 500, and blank page point to different failure layers.

2. Check DNS

Confirm the hostname resolves to the expected address. If DNS was recently changed, compare authoritative records with what recursive resolvers return. An application server cannot fix traffic that never reaches it.

3. Check the network and TLS path

Verify the expected ports are reachable and that the TLS certificate covers the requested hostname and has not expired. If a proxy or CDN sits in front of the origin, test the origin separately when possible.

4. Check the web server and application

Look at the HTTP status code and the relevant web-server and application logs. Confirm the application process is running and listening where the proxy expects it.

Avoid restarting everything before collecting evidence. A restart can temporarily hide a failure and erase useful context.

5. Check dependencies and resources

A healthy web process may still fail because the database is unavailable, disk space is exhausted, memory pressure killed a process, a filesystem became read-only, or an external dependency is timing out.

Check CPU, memory, disk and inode usage, database connectivity, queues, and recent deployment or configuration changes.

6. Restore service, then preserve the lesson

Once service is stable, write down the cause, detection gap, and prevention. If a full disk caused the outage, restarting the application is not the complete fix; monitoring and log-retention changes are part of it.