What Is Synthetic Monitoring? A Plain-Language Guide

What Is Synthetic Monitoring?

Synthetic monitoring (also called external monitoring) checks your website or service from the outside, simulating the experience of a real user accessing your site over the internet. Instead of relying on the server to report its own health, synthetic monitoring sends requests through the same network path your visitors use.

This distinction matters. A server can be running perfectly while a misconfigured DNS record or an expired SSL certificate makes the site completely unreachable. Synthetic monitoring catches these failures because it looks at the site the same way your users do.

Synthetic Monitoring vs Internal Monitoring

Server monitoring broadly falls into two categories:

For web agencies managing client sites, synthetic monitoring is the natural starting point. You do not need server access to set it up, meaning you can add monitoring for a client site on day one without waiting for server credentials or client IT approval.

The Four Core Synthetic Checks

Miterl's synthetic monitoring covers four check types: HTTP, Ping, SSL, and WHOIS (domain expiry).

HTTP Monitoring -- Is the Page Loading?

HTTP monitoring sends a request to a URL and verifies that the server responds with an expected status code, body content, or response time. This is the most fundamental external check.

# Manual HTTP check using curl
curl -o /dev/null -s -w "Status: %{http_code}\nResponse time: %{time_total}s\n" \
  https://example.com

Miterl automates this exact check at intervals as short as one minute. The moment a status code changes from 200 or the response time exceeds a threshold, an alert fires immediately.

Ping Monitoring -- Is the Server Reachable?

Ping sends an ICMP packet to the server and waits for a reply. It operates below the application layer, confirming that the server itself is alive on the network. Used alongside HTTP monitoring, Ping helps you quickly distinguish between an application crash and a full server outage.

SSL Monitoring -- Is the Certificate Valid?

SSL monitoring checks certificate expiry dates, chain validity, and domain name matches.

# Check SSL certificate expiry manually
echo | openssl s_client -connect example.com:443 2>/dev/null \
  | openssl x509 -noout -enddate

An expired certificate triggers a full-page browser warning that effectively blocks all visitors. Miterl alerts you well before expiry so you can renew without any downtime. This is especially valuable when managing dozens of client sites where manual tracking becomes error-prone.

WHOIS Monitoring -- Is the Domain About to Expire?

WHOIS monitoring tracks your domain's registration expiry date. An expired domain takes the entire site offline no matter how healthy the server is, and nobody can reach it until the registration is renewed. This failure is easy to miss because it has nothing to do with your application or infrastructure. For agencies that manage client domains, WHOIS monitoring prevents the catastrophic outage of a forgotten renewal. Use whois_expiry_alert_days to choose how many days before expiry the alert fires.

Why Synthetic Monitoring Is Enough for Most Agencies

Internal monitoring tools like Zabbix or Prometheus are powerful, but they require agent installation on each server, depend on server operating system compatibility, and carry ongoing maintenance costs. For an agency managing client websites:

• Clients may not grant server access
• Each server environment has different setup requirements
• Overhead grows with every additional client

Synthetic monitoring requires nothing but a URL. It directly answers the only question that matters to your client: is the site working right now?

Combining Synthetic and Internal Monitoring

When you manage VPS or dedicated servers for clients, combining both approaches strengthens your ability to diagnose root causes quickly.

A typical workflow looks like this:

1. Synthetic monitoring detects the site is down
2. Internal monitoring confirms CPU or memory is exhausted
3. You resolve the resource issue and confirm the site is back up via synthetic monitoring

For agencies just starting out, the recommended approach is to begin with synthetic monitoring and add internal monitoring only when you manage the underlying infrastructure.

Setting Up Synthetic Monitoring with Miterl

Miterl supports all four check types (HTTP, Ping, SSL, WHOIS) from a single dashboard. The REST API makes it easy to add monitors programmatically as you onboard new clients.

# Add a new HTTP monitor via the Miterl API
curl -X POST https://miterl.com/api/v1/monitors \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "client-a Production",
    "url": "https://client-site.example.com",
    "type": "http",
    "interval_seconds": 60,
    "alert_contact_ids": [1, 2]
  }'

alert_contact_ids takes an array of integer alert-contact IDs. Create your alert contacts in the dashboard, then fetch their IDs with GET /api/v1/alert-contacts. Changing the type field to "ping", "ssl", or "whois" uses the same syntax for each check type. You can organize monitors by client in the dashboard.

Recommended Setup for Agencies

Summary

Synthetic monitoring watches your website from the outside, the same vantage point your users have. It requires no server access, can be set up in minutes, and directly measures what matters most: whether real visitors can reach and use the site.

• Synthetic monitoring checks availability from the internet, not from inside the server
• HTTP, Ping, SSL, and WHOIS are the four core check types
• Agencies benefit most because setup requires no server credentials
• Combining synthetic and internal monitoring accelerates root cause analysis

Configure your first monitors using the documentation. Try all check types on a free plan. To learn how to bundle monitoring into client maintenance contracts, read Why Web Agencies Should Include Uptime Monitoring in Maintenance Contracts. For a side-by-side tool comparison, see the uptime monitoring comparison guide.