Attrac vs Justuno: Shopify Performance Comparison
Both apps score Grade A — Justuno has the edge with 3 ms vs 4 ms desktop CPU execution.
Both apps provide popup, email capture, and conversion optimization 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 | Attrac | Justuno | Faster |
|---|---|---|---|
| Overall Grade | A | A | Tie |
| JS Payload | 12.34 KB | 4.44 KB | Justuno |
| CPU Desktop | 4 ms | 3 ms | Justuno |
| CPU Mobile | 26 ms | 17 ms | Justuno |
| Layout Shift | 0.0 | 0.0 | Attrac |
Mobile CPU measured with 4× CDP throttle (mid-range Android). Tested 2026-05-30.
Justuno — The Faster Option (Grade A)
Justuno scores Grade A with a JS payload of 4.44 KB and 3 ms desktop CPU execution. Mobile CPU: 17 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 Justuno speed report →
Attrac — The Heavier Option (Grade A)
Attrac scores Grade A with a JS payload of 12.34 KB and 4 ms desktop CPU execution. Mobile CPU: 26 ms. Performance is acceptable but worth monitoring, particularly on stores with high mobile traffic share.
View full Attrac speed report →
When to Choose Attrac
- 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
When to Choose Justuno
- 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
Result: Comparable — Both apps score Grade A — Justuno has the edge with 3 ms vs 4 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.