Why Azure certificate expiry alerts still need an external check
Azure-hosted apps can use App Service managed certificates, imported PFX certificates, Front Door managed certificates, Application Gateway listeners, or Key Vault certificates. Each has different renewal and alert behaviour. The safest pattern is to combine Azure-native notifications with a public TLS check against the hostname your customers use.
Certimon checks the live certificate from outside Azure and sends a Telegram reminder before expiry. That catches the practical failure modes: a certificate renewed in Key Vault but not deployed, a stale binding on App Service, a custom domain pointing at the wrong endpoint, or a manual certificate that nobody replaced.
Fast setup with Certimon
Open @CertimonBot on Telegram and add your public Azure hostname:
/remind domain.com 30
Replace domain.com with the externally visible hostname, such as www.example.com, api.example.com, or a custom domain routed through Azure Front Door.
Azure-native options to pair with external reminders
App Service custom domains
App Service managed certificates are intended to renew automatically, but imported certificates and some custom binding situations need owner attention. Monitor the live hostname with Certimon so you know whether the endpoint is serving a certificate that expires soon.
Azure Front Door
Front Door managed certificates reduce manual work, while bring-your-own-certificate setups depend on Key Vault and correct Front Door configuration. An external reminder verifies the public edge hostname rather than only the certificate object.
Key Vault certificates
Key Vault can alert on near-expiry certificate objects and integrate with Event Grid or Azure Monitor. Keep those alerts, then use Certimon to confirm the renewed certificate is actually deployed to the public domain.
Externally visible domains
If customers can open the HTTPS site from the internet, Certimon can usually monitor it. This includes Azure-hosted web apps, APIs, CDN or Front Door endpoints, and domains backed by Azure DNS.
Important caveats
- Private endpoints: Certimon cannot check VNet-only hosts, private DNS names, internal load balancers, or firewalled endpoints that are not reachable from the public internet.
- Hostname matters: Monitor the exact public name users visit. A certificate may be valid on example.azurewebsites.net but expired on www.example.com.
- External checks complement Azure: Keep Azure Monitor, Key Vault lifecycle notifications, and operational alerts. Certimon is an independent safety net, not a replacement for fixing failed renewals.
FAQ
Does Azure App Service notify me before custom domain certificates expire?
Azure-managed App Service certificates are designed to renew automatically, but custom or imported certificates still need monitoring. Use Azure alerts where available and add an external check like Certimon for public hostnames.
How do I monitor Azure Front Door SSL certificate expiration?
Managed Front Door certificates renew automatically, while BYOC certificates depend on the certificate source such as Key Vault. Monitor the public hostname externally so renewal or binding issues are caught before users see TLS errors.
Can Azure Key Vault alert on certificate expiry?
Yes. Key Vault certificates can emit lifecycle events and near-expiry notifications. That does not prove the live public endpoint is serving the renewed certificate, so external endpoint monitoring is still useful.
Does this work for every externally visible Azure domain?
Certimon works with public TLS endpoints where it can connect to the hostname and read the certificate. It is useful for App Service, Front Door, APIs, and other Azure-hosted HTTPS domains that are reachable from the internet.
Can Certimon monitor private or internal Azure endpoints?
No. Private VNet-only, internal load balancer, or firewall-restricted hosts are not visible unless they have a public hostname reachable from the internet.