GrowthBook vs Zephyr DataLayer: Shopify Performance Comparison
Both apps score Grade B — GrowthBook has the edge with 3 ms vs 16 ms desktop CPU execution.
Both apps provide heatmaps, session recording, and analytics functionality for Shopify stores. This page presents StackConflict’s independent lab results for both — measured in a clean-room environment with no other apps installed.
Head-to-Head Metrics
| Metric | GrowthBook | Zephyr DataLayer | Faster |
|---|---|---|---|
| Overall Grade | B | B | Tie |
| JS Payload | 39.98 KB | 106.96 KB | GrowthBook |
| CPU Desktop | 3 ms | 16 ms | GrowthBook |
| CPU Mobile | 4 ms | 54 ms | GrowthBook |
| Layout Shift | 0.0006 | 0.0 | Zephyr DataLayer |
Mobile CPU measured with 4× CDP throttle (mid-range Android). Tested 2026-05-30.
GrowthBook — The Faster Option (Grade B)
GrowthBook scores Grade B with a JS payload of 39.98 KB and 3 ms desktop CPU execution. Mobile CPU: 4 ms. It passes every StackConflict threshold for payload, CPU, and layout stability — making it safe to install on any storefront including mobile-first stores where Time-to-Interactive directly impacts conversion.
View full GrowthBook speed report →
Zephyr DataLayer — The Heavier Option (Grade B)
Zephyr DataLayer scores Grade B with a JS payload of 106.96 KB and 16 ms desktop CPU execution. Mobile CPU: 54 ms. Performance is acceptable but worth monitoring, particularly on stores with high mobile traffic share.
View full Zephyr DataLayer speed report →
When to Choose GrowthBook
- You need its specific features and can monitor its mobile impact
- Your other apps are lightweight (Grade A) so there is headroom
- You are on desktop-skewed traffic where CPU cost matters less
When to Choose Zephyr DataLayer
- You need its specific features and can monitor its mobile impact
- Your other apps are lightweight (Grade A) so there is headroom
- You are on desktop-skewed traffic where CPU cost matters less
Performance Verdict
Result: Comparable — Both apps score Grade B — GrowthBook has the edge with 3 ms vs 16 ms desktop CPU execution.
About This Test
StackConflict measures each Shopify app in an isolated clean-room environment — a single development store, no other scripts, Playwright-controlled browser. V8 CPU cost is the ScriptDuration delta before and after injection. CLS is captured from the same browser session. Results represent the median of three independent runs with outliers removed.
Data from the StackConflict Lab. Last updated 2026-05-30.