Meta Conversions API (CAPI) Param Builder vs WCT (Wishlist & Cart Tracking): Shopify Performance Comparison
WCT (Wishlist & Cart Tracking) wins with Grade A vs Grade B — a one-grade performance difference that compounds on mobile devices.
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 | Meta Conversions API (CAPI) Param Builder | WCT (Wishlist & Cart Tracking) | Faster |
|---|---|---|---|
| Overall Grade | B | A | WCT (Wishlist & Cart Tracking) |
| JS Payload | 54.69 KB | 29.0 KB | WCT (Wishlist & Cart Tracking) |
| CPU Desktop | 9 ms | 12 ms | Meta Conversions API (CAPI) Param Builder |
| CPU Mobile | 37 ms | 35 ms | WCT (Wishlist & Cart Tracking) |
| Layout Shift | 0.0 | 0.0005 | Meta Conversions API (CAPI) Param Builder |
Mobile CPU measured with 4× CDP throttle (mid-range Android). Tested 2026-05-31.
WCT (Wishlist & Cart Tracking) — The Faster Option (Grade A)
WCT (Wishlist & Cart Tracking) scores Grade A with a JS payload of 29.0 KB and 12 ms desktop CPU execution. Mobile CPU: 35 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 WCT (Wishlist & Cart Tracking) speed report →
Meta Conversions API (CAPI) Param Builder — The Heavier Option (Grade B)
Meta Conversions API (CAPI) Param Builder scores Grade B with a JS payload of 54.69 KB and 9 ms desktop CPU execution. Mobile CPU: 37 ms. Performance is acceptable but worth monitoring, particularly on stores with high mobile traffic share.
View full Meta Conversions API (CAPI) Param Builder speed report →
When to Choose Meta Conversions API (CAPI) Param Builder
- 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 WCT (Wishlist & Cart Tracking)
- You are running a mobile-heavy store and Core Web Vitals matter
- You want to stack multiple apps without worrying about combined JS cost
- Conversion rate optimisation is a key priority
Performance Verdict
Winner: WCT (Wishlist & Cart Tracking) — WCT (Wishlist & Cart Tracking) wins with Grade A vs Grade B — a one-grade performance difference that compounds on mobile devices.
Install WCT (Wishlist & Cart Tracking) →
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 2026-05-31.