TrackJS — Performance Grade A
Lightweight — zero friction
TrackJS is a page speed optimization app for Shopify that scores Grade A in StackConflict’s independent performance lab — placing it among the top tier apps in the Performance category. With a featherweight JavaScript bundle that downloads in milliseconds on any connection (28.61 KB compressed) and negligible main-thread time — it will not compete with your theme or checkout scripts for CPU (4 ms desktop), it adds minimal friction to the storefront experience.
On mobile devices StackConflict’s 4× throttle pass measured just 18 ms (0.02s) — a direct measurement on a simulated mid-range Android device. This negligible overhead means TrackJS will not meaningfully affect your store’s Time-to-Interactive or Core Web Vitals scores. Merchants running multiple apps can safely stack TrackJS without it becoming the bottleneck in their combined performance budget.
Verdict (Grade A — Lightweight): TrackJS by TrackJS is a safe choice from a Shopify site speed perspective. It passes all StackConflict thresholds for payload, CPU, and layout stability. Install it with confidence on any storefront, including high-traffic mobile-first stores where JavaScript overhead directly influences Add-to-Cart conversion rates and Google’s Core Web Vitals ranking signals.
Lab Results
| Metric | Value | Grade |
|---|---|---|
| JS Payload | 28.61 KB | A |
| CPU Execution (desktop) | 4 ms | A |
| CPU Execution (mobile) | 18 ms | — |
| Cumulative Layout Shift | 0.0006 | A |
| Overall Grade | — | A |
| Category | Performance | — |
| Last tested | 2026-05-30 | — |
Lab Verdict
Passes all performance thresholds. Safe to install on mobile-heavy stores.
Grading Scale
Each app is graded across three independent dimensions. The final grade is the worst of the three — no dimension can be hidden by a good score elsewhere.
| Grade | Payload | CPU (desktop) | CLS | Risk |
|---|---|---|---|---|
| A | ≤ 30 KB | ≤ 50 ms | < 0.1 | Lightweight — zero friction |
| B | ≤ 150 KB | ≤ 150 ms | < 0.25 | Acceptable — monitor on mobile |
| C | ≤ 500 KB | ≤ 500 ms | < 0.5 | Heavy — high conversion risk |
| D | > 500 KB | > 500 ms | ≥ 0.5 | Critical — avoid on mobile stores |
About This Test
StackConflict measures app performance in a clean-room environment. Each app’s JavaScript bundle is injected into an owned Shopify development store via a Playwright-controlled browser, with no other third-party apps installed. V8 CPU cost is the ScriptDuration delta measured before and after injection on the same live page. Mobile CPU estimate applies the 4× Lighthouse slowdown factor to approximate real-device impact.
Data sourced from the StackConflict Lab. Last updated 2026-05-30.