Network Diagnostics
When a site goes down, SiteBrief automatically runs a layered network diagnosis — DNS → TCP → TLS → HTTP — so you see exactly which layer failed instead of a vague 'site is down'.
The problem it solves
"The site is down" isn't actionable. Is it DNS? An expired certificate? The server refusing connections? A 500 error from the app? Network Diagnostics walks every layer of the connection in order and tells you precisely where it broke — turning a 3 AM page into a clear next step.
The layers it checks
| Layer | What it verifies | A failure here means |
|---|---|---|
| DNS | The domain resolves to an IP address | Domain expired, nameserver issue, or DNS misconfiguration |
| TCP | A connection opens on the target port (80/443) | Server is offline, firewall blocking, or wrong port |
| TLS | The SSL/TLS handshake completes | Expired/invalid certificate or unsupported protocol |
| HTTP | The server returns a valid HTTP response | App-level error (5xx), redirect loop, or timeout |
ℹ️
Note:Diagnostics run automatically the moment a downtime is detected, and you can also trigger them on demand from the site detail page.
How to read the result
The first failing layer is the root cause — everything after it is a consequence. For example, if DNS fails, TCP/TLS/HTTP will all fail too, but the fix is at the DNS layer.
| First failing layer | Where to look |
|---|---|
| DNS | Domain registrar / DNS provider — check the domain isn't expired and records are correct |
| TCP | Hosting / firewall — is the server running and is the port open? |
| TLS | SSL certificate — renew it or fix the chain (see SSL & Domain docs) |
| HTTP | The application — check server logs for 5xx errors or recent deploys |
Frequently asked questions
Do I need to configure anything?
No. Network Diagnostics run automatically on every detected outage. You can also run them manually from the site page at any time.
What's the difference between this and multi-location checks?
Multi-location checks answer "is it really down?" by verifying from several regions. Network Diagnostics answer "why is it down?" by isolating the failing layer. They complement each other.
Is it available on the Free plan?
Yes — layered diagnostics are available on all plans, including Free.