Why Choose Synthetic Monitoring Instead of Real User Monitoring?

Choose synthetic monitoring instead of real user monitoring when you need to check whether a known page, API, flow, or system is working before real users run into a problem.

Choose real user monitoring, or RUM, when you need to understand what actual users experienced across real devices, browsers, networks, locations, and journeys.

That is the whole decision. Synthetic monitoring is best for proactive checks and controlled baselines. RUM is best for real-world experience and impact. Most mature teams eventually use both, but if you are asking which one to choose first, start with the question you need answered.

Synthetic monitoring vs RUM: the decision table

Use this table before comparing tools.

If you need to know…	Choose	Why
Is the site, app, API, or key flow working right now?	Synthetic monitoring	It runs on a schedule without waiting for users
Did real users have a bad experience?	RUM	It collects data from actual user sessions
Did a release break a known path?	Synthetic monitoring	It can run before or immediately after deployment
Are mobile users in a certain country struggling?	RUM	It shows real devices, locations, browsers, and networks
Is uptime or SLA coverage the priority?	Synthetic monitoring	It gives predictable, alertable checks
Are Core Web Vitals bad for real users?	RUM	Field data shows how users actually experienced the page
Is an API or backend slowdown affecting users?	Use both	Synthetic confirms the endpoint or flow; RUM shows user impact
Is the site low traffic or newly launched?	Synthetic monitoring first	RUM may not have enough data yet

The short version:

• Use synthetic monitoring to catch known problems early.
• Use RUM to understand real-world user experience.
• Use both when the experience is important enough that you need proactive alerts and real-user context.

That is the quick answer. The next sections unpack the differences in more detail so you can make the call without guessing.

Real user monitoring vs synthetic monitoring: what is the difference?

RUM and synthetic monitoring answer different questions.

RUM measures what happened to real users across the browsers, networks, devices, and geographies that actually visited.

Synthetic monitoring measures what a scripted probe or browser experienced under fixed conditions, which creates a clean baseline that works before launch, during quiet hours, and at 3 a.m.

	RUM	Synthetic monitoring
How is data collected?	Passively, from real user sessions through a browser or mobile SDK	Actively, by scripted probes such as HTTP checks, API transactions, and browser journeys
Availability alerting	Weak when there is no traffic, because no traffic means no user data	Strong, because probes run on a schedule and fail within one or two check intervals
SLA verification	Noisier, because user device and network variance are included	Stronger, because a fixed probe, browser, and location create a more stable baseline
Geographic coverage	Wherever real users are, in the proportions they actually visit	Only the probe locations you configure
Pre-production testing	Not possible, because RUM needs real traffic	Strong, because the same checks can run against staging or pre-release environments
Long-tail experience	Strong, because it captures real devices, networks, paths, and edge cases	Weak, because it only tests the paths someone scripted
Cost and data volume	Scales with sessions, events, replay settings, sampling rate, and retention	Scales with checks, frequency, locations, and journey complexity

That table is the decision in miniature. Synthetic monitoring is better when you need a controlled, repeatable answer. RUM is better when you need real-world variance and user impact.

What is real user monitoring?

Real user monitoring is the passive collection of performance and experience data from real user sessions. A browser script or mobile SDK records what happened during a visit, then sends that data to a collection endpoint for analysis.

RUM can capture page loads, Core Web Vitals, resource timings, JavaScript errors, network timings, user journeys, and conversion context, depending on the tool and setup.

Common RUM tools include Datadog RUM, New Relic Browser, Sentry, SpeedCurve RUM, Elastic RUM, Cloudflare Web Analytics, Raygun, and DebugBear RUM.

RUM is strongest when you need to understand reality: which users were affected, on which devices, in which browsers, on which networks, and how much it mattered.

What is synthetic monitoring?

Synthetic monitoring runs scripted probes against a system on a schedule from controlled locations. Those probes can be simple HTTP uptime checks, API transactions, or full browser journeys.MDN describes synthetic monitoring as a controlled, lab-style approach that uses scripted traffic rather than actual user sessions.

Common synthetic monitoring tools include UptimeRobot, Pingdom, Uptrends, Checkly, Datadog Synthetic Monitoring, New Relic Synthetic Monitoring, Elastic Synthetics, and SpeedCurve synthetic testing. Some are simple uptime and SSL monitors. Others, depending on the platform and plan, can run browser-based checks, API checks, or scripted flows like login and checkout.

Because the probe, script, network, and location are controlled, every run is easier to compare with the previous run. That makes synthetic monitoring useful for alerting, baseline tracking, release checks, and SLA-style reporting.

Check cadence matters. A lightweight uptime check might run every minute. A full browser journey might run every 5, 10, or 15 minutes because rendering pages and executing scripts costs more than a simple ping. The more locations, journeys, and assertions you add, the more coverage you get, but the more checks you pay for and maintain.

When to choose synthetic monitoring instead of RUM

Choose synthetic monitoring when the risk is predictable, and you can define what “working” means.

That includes:

• A homepage should load.
• A checkout flow should complete.
• A login page should work.
• An API should return the expected status and response.
• A landing page should stay fast enough.
• SSL, DNS, redirects, and uptime should remain healthy.
• A release should not break a critical flow.

Synthetic monitoring is useful because it does not wait for traffic. It checks the thing you care about on a schedule.

That makes it the better first choice in these situations.

1. You are launching a new page, feature, or flow

Start with synthetic monitoring before launch.

A new page or feature has no real-user history yet. RUM cannot tell you much until people start using it. Synthetic tests can run in staging, in CI/CD, or immediately after release so you can catch obvious regressions before users see them.

Use synthetic monitoring for:

• New landing pages
• Checkout changes
• Login or signup changes
• Pricing page changes
• UI revamps
• New API endpoints
• Critical user journeys

After launch, add RUM if the page or flow gets enough traffic. RUM will show whether the controlled test matched the real world.

This is one of the cleanest ways to use both: synthetic before release, RUM after release.

2. You need uptime, availability, or SLA monitoring

Choose synthetic monitoring when you need to know whether something is available right now.

Synthetic checks are predictable and alertable. If a site goes down at 3 a.m., a synthetic uptime check can alert you before a real user reports it. If an API starts returning errors, an API check can catch it on the next scheduled run.

Use synthetic monitoring for:

• Uptime checks
• SSL certificate checks
• DNS checks
• Redirect checks
• API availability
• Basic page availability
• SLA or SLO monitoring

RUM can tell you who was affected after an incident. It can show how many sessions failed, which regions were hit, and how bad the experience was. But RUM is not the best first signal for minute-by-minute availability. If users cannot reach the site, there may be no complete user session to report.

The practical setup is: synthetic monitoring alerts you that something broke, RUM helps you understand user impact.

3. The site or page has low or uneven traffic

Choose synthetic monitoring first when there is not enough real traffic for RUM to produce useful signals.

This applies to:

• New websites
• B2B websites
• Local business sites
• Niche ecommerce stores
• Campaign landing pages
• Long-tail product pages
• Low-traffic support or documentation pages
• Early-stage SaaS products

RUM needs real users. If only a handful of people visit a page each day, it may take too long to know whether a problem is real. Google Search Console’s Core Web Vitals report has a similar limitation: URL groups without enough real-world usage data may not appear.

That does not mean the page is healthy. It means there may not be enough field data.

Synthetic monitoring solves a different problem: it can check important pages and flows even when nobody is visiting.

4. You need repeatable regression checks

Synthetic monitoring is better when you want to compare the same thing over time.

Because the test is controlled, changes are easier to spot. If the same browser check runs from the same location on the same flow every 10 minutes, a sudden slowdown after a deploy is easier to investigate.

Use synthetic monitoring for:

• Release gates
• CI/CD performance checks
• Staging checks
• Post-deploy smoke tests
• Known user flow checks
• API regression checks
• Third-party script or dependency checks

RUM is better at showing the messy real world, but that messiness can make regression detection harder. Synthetic monitoring gives you a cleaner baseline.

5. You need to test a known user journey

Choose synthetic monitoring when you can describe the path you need to test.

For example:

• Visit the homepage.
• Search for a product.
• Add an item to cart.
• Start checkout.
• Confirm the checkout page loads.

Or:

• Visit the login page.
• Submit test credentials.
• Confirm the dashboard loads.

Not every monitoring tool supports full scripted flows, and some flows should not be tested with real transactions unless you have a safe test setup. But when your tool supports it, synthetic journey monitoring is a good way to check known paths repeatedly.

The limitation is obvious: synthetic monitoring only tests the path you wrote. If real users take a different route, use a different device, or hit a browser-specific issue, synthetic checks may stay green while users struggle.

That is where RUM becomes useful.

When RUM is the better choice

Choose RUM when the problem is not “is this known path working?” but “what are real users actually experiencing?”

RUM is stronger when you need to see variation:

• Devices
• Browsers
• Operating systems
• Network speeds
• Countries and regions
• Page types
• User journeys
• JavaScript errors
• Conversion impact

Synthetic monitoring usually runs from known locations and controlled environments. RUM captures the real environment. If you’re looking for a RUM tool, check out our guide on choosing the right real user monitoring tool.

1. Users complain, but synthetic checks are green

This is the classic RUM use case.

Your uptime checks pass. Your Lighthouse score looks fine. Also, your synthetic checkout test works. But users still complain that the site feels slow, buttons freeze, or checkout fails on mobile.

That can happen because real users bring conditions your synthetic tests did not cover:

• Slower phones
• Older browsers
• Weak mobile networks
• Regional CDN issues
• Ad scripts
• Browser extensions
• Cookie banners
• Third-party tags
• Different page paths
• Different release versions

RUM helps you find those patterns. It can show that the issue is not “the site is slow for everyone,” but “users on midrange Android devices in one region are seeing poor INP.”

2. You need real Core Web Vitals data

Synthetic tools can estimate Core Web Vitals in lab conditions. Lighthouse, for example, is useful for diagnosing performance issues. If you run Lighthouse repeatedly in CI or on a schedule, it becomes synthetic-style regression testing.

But Core Web Vitals are ultimately about real user experience. Lighthouse and CrUX sit on different sides of this split: Lighthouse is lab data, while CrUX is field data from real Chrome users.

Use RUM when you need to understand:

• Real LCP across devices and networks
• Real CLS across page templates
• Real INP across user interactions
• Which pages hurt the most users
• Which performance problems affect conversion

Synthetic data is useful for diagnosis. RUM is better for real-world prioritization.

If your primary goal is Core Web Vitals RUM, WebYes helps you monitor LCP, CLS, and INP using data from real visitors. You can track performance trends across pages, devices, and over time.

3. You need regional, browser, device, or network detail

Choose RUM when the issue depends on who the user is and where they are.

Synthetic monitoring can run from multiple regions, but it still uses a controlled setup. RUM shows the actual spread of users.

RUM is the better fit for questions like:

• Are users in one country seeing slower pages?
• Is Safari behaving differently from Chrome?
• Are low-end Android devices struggling?
• Are mobile users seeing worse INP?
• Are users on slow networks abandoning checkout?
• Did a release affect only one browser or app version?

Synthetic monitoring can help reproduce the issue once you know where to look. RUM is often how you find the affected segment.

4. You need to measure user impact

RUM is better when the important question is not just “did something fail?” but “how many users did it affect, and how badly?”

Synthetic monitoring might tell you a checkout check failed for three minutes. RUM can show whether that failure affected 2 sessions or 2,000 sessions.

RUM can also help prioritize fixes. A slow page with little traffic may matter less than a slightly less slow page that affects thousands of users and drives revenue.

Use RUM for:

• Impact analysis
• Conversion impact
• User journey analysis
• Release impact
• Browser and device segmentation
• Error frequency and distribution

Synthetic monitoring finds predictable failures. RUM helps you decide how much they mattered.

When to use both synthetic monitoring and RUM

Use both when the experience is business-critical.

That includes:

• Ecommerce checkout
• Signup and login
• SaaS dashboards
• Booking flows
• Payment flows
• Lead-generation flows
• High-traffic content pages
• APIs that power important user journeys
• Regions with strict reliability expectations

The two tools work best as a pair:

	Synthetic monitoring does this	RUM does this
Availability	Alerts when the page, API, or flow fails	Shows who was affected
Release safety	Catches regressions before users see them	Confirms the release worked in the real world
Performance	Provides a stable baseline	Shows real device, browser, and network experience
Backend/API issues	Confirms endpoint or flow health	Shows frontend impact on real sessions
Core Web Vitals	Helps diagnose in lab conditions	Shows real-user field performance

The best setup is not “synthetic or RUM.” It is usually:

1. Synthetic monitoring for known critical paths.
2. RUM for real user experience and impact.
3. Logs, traces, and backend metrics to explain why the issue happened.

ClickHouse’s framing is useful here: RUM tells you what real users experienced, while synthetic monitoring tells you what scripted probes experienced. You need both when you care about alerting, coverage, and diagnosis at the same time.

Final recommendation

Synthetic monitoring is the better first choice when you need proactive confidence that known pages, APIs, and flows are working.

RUM is the better choice when you need real-world truth: devices, browsers, geographies, networks, user journeys, and actual impact.

If you are choosing only one to start, choose based on the risk:

• Risk of something breaking before anyone notices? Start with synthetic monitoring.
• Risk that real users are having a bad experience you cannot see? Start with RUM.
• Risk is business-critical? Use both.

That is the cleanest way to avoid buying the wrong monitoring tool. Do not choose synthetic monitoring because it sounds simpler. Do not choose RUM because it sounds more real. Choose the one that answers the question you actually need answered.