What Is Synthetic Monitoring? A Plain-English Guide

When something goes wrong on your website, you want to know before your users do. But how do you detect problems without waiting for a real user to encounter them?

That's the job of synthetic monitoring — a technique that simulates user interactions with your website using automated scripts, running continuously from external locations, 24 hours a day.

Synthetic Monitoring Explained

The word "synthetic" here means artificial or simulated — as opposed to monitoring that analyses real user traffic. A synthetic monitor doesn't wait for a user to visit your site. It acts as a user, making requests to your site on a schedule and checking whether the expected results come back.

The simplest form of synthetic monitoring is a basic uptime check: every minute, a monitoring server sends an HTTP request to your URL and checks that you get a valid response. If the response fails or takes too long, an alert fires.

More advanced forms of synthetic monitoring include:

• API monitoring — sending requests to your API endpoints and verifying responses
• Multi-step transaction monitoring — simulating a full user journey (login, browse, checkout)
• Browser monitoring — using a headless browser to fully execute your page's JavaScript and check the rendered result

For most websites and web applications, HTTP uptime monitoring is the most important form of synthetic monitoring to have in place. It's fast to set up, inexpensive, and catches the most common failure modes.

Synthetic Monitoring vs. Real User Monitoring (RUM)

These two approaches complement each other:

	Synthetic Monitoring	Real User Monitoring
When it runs	On a schedule, 24/7	Only when real users visit
Detects issues	Even when no users are online	Only when users are affected
Data source	Simulated requests	Real browser sessions
Best for	Uptime detection, availability	Performance analysis, UX issues
Requires traffic	No	Yes

Synthetic monitoring is proactive — it finds problems before users hit them. Real user monitoring is reactive — it analyses problems that already affected real sessions.

For uptime and availability monitoring, synthetic monitoring is the right tool. You can't afford to wait for a real user to visit your 404 page to find out your site is down.

How Synthetic Uptime Monitoring Works

A typical synthetic uptime check:

1. A monitoring server (in a data centre, often in multiple locations worldwide) sends an HTTP/HTTPS request to your URL
2. The request is timed — how long does it take to receive the first byte and the complete response?
3. The response is checked — is the status code correct? Does the response body contain expected content?
4. Results are recorded — response time, status code, and pass/fail are logged
5. If the check fails, an alert is sent via email, SMS, or Slack

This cycle repeats on your configured interval — every minute, every 5 minutes, etc.

Multi-Location Synthetic Monitoring

Running checks from a single location gives you one perspective. Running checks from multiple locations gives you a clearer picture:

• If checks fail from all locations → global outage affecting all users
• If checks fail from one location only → regional issue; users in that area are affected
• If checks are slow from some locations → CDN or routing issue causing latency for distant users

Multi-location monitoring is an important part of a complete synthetic monitoring setup, especially for websites with an international audience.

What Synthetic Monitoring Catches

Synthetic monitoring is particularly good at detecting:

• Complete outages — server down, hosting failed, DNS broken
• Slow responses — your site is up but responding in 8 seconds rather than 0.8 seconds
• Broken content — server returns 200 OK but the body is empty or contains an error page
• SSL certificate issues — certificate expired or misconfigured
• API failures — backend endpoints returning errors or timing out
• Redirect loops — requests cycling endlessly through redirects

What it doesn't catch as well: visual rendering bugs, JavaScript errors in the browser, or subtle UX issues. For those, you'd need real user monitoring or browser-based synthetic tests.

Synthetic Monitoring for APIs

APIs are ideal targets for synthetic monitoring. Unlike websites, APIs have well-defined contracts: send this request, get back this response. A synthetic API monitor:

1. Sends a request to your API endpoint (with appropriate headers and body)
2. Checks that the response status code matches expectations (200, 201, etc.)
3. Optionally verifies the response body contains expected fields
4. Records the response time

This gives you continuous verification that your API is functioning correctly — independent of whether any real client application is actively using it. See what is API monitoring for a deeper look.

Setting Up Synthetic Monitoring

Getting started with synthetic monitoring is straightforward:

1. Choose a monitoring tool — Domain Monitor provides HTTP uptime monitoring as its core feature
2. Add the URLs you want to monitor
3. Set your check interval (1 minute recommended for production)
4. Configure alert thresholds and notification channels
5. Enable multi-location checks

A basic synthetic monitoring setup for most websites takes under 10 minutes to configure and provides continuous coverage from that point forward.

The Value of "Always-On" Checks

The key advantage of synthetic monitoring over manual checking is continuity. You can't manually check your website every minute around the clock, but an automated synthetic monitor can. Issues that occur at 3am, during deployments, or in a geographic region where you have no team members are all caught the same way as issues during business hours.

This "always-on" property is what makes synthetic monitoring the foundation of any serious website monitoring strategy.

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Set up always-on synthetic monitoring at Domain Monitor.

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• "Website Monitoring vs Application Monitoring: What's the Difference?"
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