Sticky Add To Cart vs Upsellit: Shopify Performance Comparison
Both apps score Grade B — Upsellit has the edge with 10 ms vs 37 ms desktop CPU execution.
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 | Sticky Add To Cart | Upsellit | Faster |
|---|---|---|---|
| Overall Grade | B | B | Tie |
| JS Payload | 50.02 KB | 32.0 KB | Upsellit |
| CPU Desktop | 37 ms | 10 ms | Upsellit |
| CPU Mobile | 167 ms | 27 ms | Upsellit |
| Layout Shift | 0.0 | 0.0 | Sticky Add To Cart |
Mobile CPU measured with 4× CDP throttle (mid-range Android). Tested 2026-05-30.
Upsellit — The Faster Option (Grade B)
Upsellit scores Grade B with a JS payload of 32.0 KB and 10 ms desktop CPU execution. Mobile CPU: 27 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 Upsellit speed report →
Sticky Add To Cart — The Heavier 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. Performance is acceptable but worth monitoring, particularly on stores with high mobile traffic share.
View full Sticky Add To Cart speed report →
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
When to Choose Upsellit
- 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 — Upsellit has the edge with 10 ms vs 37 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.