Monster Upsells vs Sticky Add To Cart: Shopify Performance Comparison
Sticky Add To Cart wins with Grade B vs Grade C — a one-grade performance difference that compounds on mobile devices.
Both apps provide post-purchase upsell and cross-sell 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 | Monster Upsells | Sticky Add To Cart | Faster |
|---|---|---|---|
| Overall Grade | C | B | Sticky Add To Cart |
| JS Payload | 214.5 KB | 50.02 KB | Sticky Add To Cart |
| CPU Desktop | 17 ms | 37 ms | Monster Upsells |
| CPU Mobile | 76 ms | 167 ms | Monster Upsells |
| Layout Shift | 0.0 | 0.0 | Monster Upsells |
Mobile CPU measured with 4× CDP throttle (mid-range Android). Tested 2026-05-30.
Sticky Add To Cart — The Faster Option (Grade B)
Sticky Add To Cart scores Grade B with a JS payload of 50.02 KB and 37 ms desktop CPU execution. Mobile CPU: 167 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 Sticky Add To Cart speed report →
Monster Upsells — The Heavier Option (Grade C)
Monster Upsells scores Grade C with a JS payload of 214.5 KB and 17 ms desktop CPU execution. Mobile CPU: 76 ms. This places it in the heavier half of StackConflict’s benchmark dataset — merchants running mobile-first stores should evaluate whether the feature value justifies the performance tradeoff.
View full Monster Upsells speed report →
When to Choose Monster Upsells
- Its unique feature set has no lighter equivalent in StackConflict’s database
- Your store traffic is predominantly desktop
- You have already removed or lightened other heavy scripts to compensate
When to Choose Sticky Add To Cart
- 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
Winner: Sticky Add To Cart — Sticky Add To Cart wins with Grade B vs Grade C — a one-grade performance difference that compounds on mobile devices.
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.