Introduction
Simulation mode lets you explore “what-if” scenarios in your performance data without changing anything in the real world. It’s a way to test how your Core Web Vital metrics - LCP, CLS, INP, TTFB, and PLS - would look if a specific segment of your traffic performed differently. Instead of guessing which issue deserves your attention, you can model the impact instantly and make decisions backed by data.
How is Simulation useful?
Performance work often feels like chasing shadows. You see the overall LCP is high, but the real question is: what’s actually pulling that number up? And more importantly, is it worth your time to fix it?
Simulation mode helps you answer exactly that.
Imagine you’re inspecting your LCP and notice that traffic coming from a specific channel - say Email - is dragging the metric up. Everything else looks healthy, but this segment is way off. With simulation, you can test a scenario: “What if Email traffic performed better?”
You enter a new LCP value for this segment and we recalculate your overall metric using the real distribution of your existing data. If the new overall LCP drops significantly, you instantly see that fixing this issue would have good impact.
This clarity helps you:
Prioritize work based on the actual payoff
Avoid investing time in low-impact fixes
Understand which breakdowns contribute most to regression
Communicate the expected benefits of improvements to your team or stakeholders
It turns performance optimization from guesswork into a strategic, evidence-based process.
How to use it?
In Experience locate the Breakdown and value you would like to Simulate:
Select the segment you want to Simulate:
Enter a new value for this segment:
Inspect the expected outcome:
Simulation mode works for any breakdown and any supported metric, giving you a fast way to validate where your performance efforts should go next.
Moving forward
Try out Simulation mode and see how it reshapes the way you prioritize performance work. By modeling real “what-if” scenarios, you can quickly understand where improvements matter most. Give it a spin and start making decisions with sharper insight.