(What’s the difference - and why you probably need both)
If you’ve worked on a mobile app long enough, you’ve asked this question at least once:
“The app works fine for me… so why are users complaining?”
This is where monitoring comes in.
And more specifically, where Real User Monitoring (RUM) and Synthetic Monitoring enter the picture.
They sound similar.
They are not.
Let’s break them down in a way that actually makes sense for mobile apps.
First: What Problem Are We Even Solving?
Mobile apps live in the wild.
Different devices.
Different networks.
Different OS versions.
Different user behavior.
You can test all you want in staging, but the moment real users show up, reality hits differently.
Monitoring answers one core question:
“How is my app behaving when it’s actually being used?”
RUM and Synthetic Monitoring just answer that question from very different angles.
What Is Synthetic Monitoring? (The “Lab Test”)
Synthetic monitoring is when you simulate users.
You define:
- A flow (open app → login → load dashboard)
- A device or environment
- A schedule (every 5 minutes, hourly, etc.)
Then a bot runs that flow again and again.
What Synthetic Monitoring Is Great At
- Catching downtime early
- Monitoring critical paths (login, checkout, onboarding)
- Testing before users are affected
- Running checks 24/7, even when no users are active
Think of it like unit tests for your production app experience.
Where It Falls Short
- It only tests what you define
- It doesn’t reflect real user behavior
- It can’t capture edge cases you didn’t think of
If your synthetic test passes, it just means:
“The happy path works in a controlled environment.”
That’s useful - but incomplete.
What Is Real User Monitoring (RUM)? (The “Reality Check”)
Real User Monitoring watches actual users using your app.
No scripts.
No assumptions.
Just real devices, real networks, real chaos.
It captures:
- App startup time
- Screen load times
- Crashes & ANRs
- Network latency
- Device-specific issues
- OS-version quirks
What RUM Is Great At
- Seeing what users actually experience
- Catching issues you never predicted
- Understanding performance across devices & regions
- Measuring impact at scale
This is where you learn:
“The app is slow on mid-range Android devices on 4G.”
“Version 3.2 crashes mostly on iOS 17.”
“Users on poor networks are dropping off.”
That insight is gold.
Where RUM Struggles
- It only works after users are affected
- You don’t control when issues appear
- It’s reactive by nature
RUM tells you what went wrong in the real world, but not always before it happens.
So… Which One Should You Use?
Short answer: Both.
Longer answer: They solve different problems.
| Use Case | Synthetic | RUM |
|---|---|---|
| Catch issues before release | ✅ | ❌ |
| Monitor real user experience | ❌ | ✅ |
| Test critical flows | ✅ | ❌ |
| Discover unknown issues | ❌ | ✅ |
| Measure performance at scale | ❌ | ✅ |
Synthetic monitoring is preventive.
RUM is observational.
One keeps you prepared.
The other keeps you honest.
Why This Matters Especially for Mobile Apps
Mobile apps don’t fail loudly.
Sometimes:
- The app doesn’t crash
- The screen just loads slowly
- A button feels unresponsive
- A request silently retries forever
Synthetic tests may never catch this.
RUM will.
On the flip side, you don’t want to wait for users to hit a broken login flow before you notice. That’s where synthetic checks shine.
Together, they give you:
- Confidence before release
- Visibility after release
A Simple Mental Model
If you remember nothing else, remember this:
Synthetic Monitoring asks:
“Does the app work when we test it?”
Real User Monitoring asks:
“Does the app work when users use it?”
Both questions matter.
Final Thoughts
Monitoring isn’t about dashboards or metrics.
It’s about trust.
Trust that:
- Your app behaves as expected
- Your users aren’t silently suffering
- You’ll know when things go wrong
Synthetic monitoring gives you control.
Real User Monitoring gives you the truth.
And in mobile development, you need both.
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