What tools can help diagnose a 'Connection Timed Out' error?

Several tools can aid in diagnosing this issue. `ping` and `traceroute` help assess network connectivity and latency. `nslookup` is used to query DNS servers. `curl` or `wget` can be used to test the connection to an API endpoint. Network monitoring tools can provide detailed information about network traffic and performance. Browser developer tools (Network tab) can help identify failed requests and their reasons.