Performance

· 23 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

Performance-focused optimization plan with CWV assessment, top offenders, and time estimates

Mobile Desktop

Performance

Accessibility

Best Practices

SEO

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

699 ms

Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.

998 ms

Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.

7 ms

Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.

0.045

Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.

1.30 s

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

2.44 s

Page Load Progression

518 ms

1.0 s

1.6 s

2.1 s

2.6 s

3.1 s

3.6 s

4.1 s

Checks

13 PASS 5 REVIEW 2 FIX

Page Weight Budget

Action

4.2 MB transferred, 366 requests

FIX

4.2 MB transferred, 366 requests

Page weighs 8.0 MB (4.2 MB transferred)

Images are 2.1 MB — compress or use modern formats

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Got: 2.1 MB

JavaScript is 1.1 MB — consider code splitting or lazy loading

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Got: 1.1 MB

366 HTTP requests — consider bundling or reducing

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Estimated 0.89 g CO2 per page load

4.2 MB transferred

366 requests

0.89 g CO2 per page load

Images 2.1 MiB 51%

JavaScript 1.1 MiB 25%

Other 708.2 KiB 16%

Fonts 163.7 KiB 4%

HTML 111.7 KiB 3%

Other 21.1 KiB 0%

CSS 20.1 KiB 0%

Other 6.7 KiB 0%

Other 1.8 KiB 0%

Other 0 B 0%

0 2.4 MB 4.9 MB

Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Why this matters

JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.

Source: web.dev

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

HTTP Caching

Action

No cache headers

FIX

No cache headers

No Cache-Control header found

Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

ETag present — enables conditional (304) responses

No Cache-Control header

Adding a Cache-Control header can significantly improve repeat-visit performance.

Image Optimization

117 images, 0 KB saveable

REVIEW

117 images, 0 KB saveable

All images are well-optimized

117 images 2.1 MB

0 oversized -0 KB

4 legacy format

0 missing dimensions CLS risk

JS Execution Cost

966ms total JS execution

REVIEW

966ms total JS execution

Unattributable: 322ms CPU time

https://sidekicks.co.uk/: 290ms CPU time

https://sidekicks.co.uk/cdn/shop/t/96/assets/libs....: 182ms CPU time

https://sidekicks.co.uk/cdn/wpm/b264bf420w2e1681ca...: 114ms CPU time

https://sidekicks.co.uk/cdn/s/trekkie.storefront.3...: 57ms CPU time

Main Thread Breakdown

Script Evaluation 43% Other 34% Style & Layout 12% Script Parsing & Compilation 4% Parse HTML & CSS 3% Rendering 3%

Script	Total	Scripting	Parse/Compile	Party
Unattributable	322ms	19ms	0ms	1st
https://sidekicks.co.uk/	290ms	50ms	8ms	1st
https://sidekicks.co.uk/cdn/shop/t/96/assets/libs.js?v=67587959726433910401779293312	182ms	46ms	2ms	1st
https://sidekicks.co.uk/cdn/wpm/b264bf420w2e1681cap8d55857fm7d879f9cm.js	114ms	101ms	5ms	1st
https://sidekicks.co.uk/cdn/s/trekkie.storefront.387430da5919a2f9b410f0ffaf5b70216a61abfb.min.js	57ms	39ms	3ms	1st

JS Bundles

175 scripts, 67 KB unused

REVIEW

175 scripts, 67 KB unused

https://sidekicks.co.uk/cdn/wpm/b264bf420w2e1681ca...: 42 KB unused (50%)

Consider code splitting or tree shaking to reduce unused code.

https://js.smile.io/v1/vendor-core-e53549e6c38a352...: 25 KB unused (58%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 67 KB

67 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://sidekicks.co.uk/cdn/wpm/b264bf420w2e1681cap8d55857fm7d879f9cm.js	85 KB	42 KB (50%)	✓	1st
https://js.smile.io/v1/vendor-core-e53549e6c38a352bd8f6.js	44 KB	25 KB (58%)	✓	3rd
https://sidekicks.co.uk/checkouts/internal/preloads.js?locale=en-FR&default_configuration_id=1036943661	4 KB	—	✓	1st
https://shop.app/checkouts/internal/preloads.js?locale=en-FR&default_configuration_id=1036943661&shop_id=67221061933	0 KB	—	✓	3rd
https://cdn.shopify.com/shopifycloud/shop-js/modules/v2/loader.init-shop-cart-sync.en.esm.js	1 KB	—	✓	3rd
https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js	0 KB	—	✓	3rd
https://cdn.jsdelivr.net/npm/slick-carousel@1.8.1/slick/slick.min.js	0 KB	—	✓	3rd
https://cdn.shopify.com/extensions/01a18139-0b3b-7c7a-aab2-59f29fa5eae6/back-in-stock-74/assets/preorder-product-page-updater.js	4 KB	—	✓	3rd
https://cdn.shopify.com/storefront/standard-actions.js	5 KB	—	✓	3rd
https://cdn.shopify.com/shopifycloud/shop-js/modules/v2/client.init-shop-cart-sync_CywFbEu-.en.esm.js	1 KB	—	✓	3rd

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Consider code splitting or tree shaking to reduce unused code.

Why this matters

This bundle has high unused code — code-split or tree-shake to ship only what executes.

Source: web.dev / Lighthouse coverage

Main HTML Cache-Control

No Cache-Control header on main HTML response

REVIEW

No Cache-Control header on main HTML response

Main HTML response has no Cache-Control header

Without an explicit Cache-Control, browsers fall back to heuristic caching (~10% of Last-Modified age). Set `Cache-Control: no-cache` or `max-age=300` for HTML to control freshness explicitly -- prevents stale auth state and SPA shell drift.

Page Weight Inventory

Action

366 resources · 4.2 MB · 67 KB savings available

REVIEW

366 resources · 4.2 MB · 67 KB savings available

Page weight 4.2 MB exceeds 1 MB target by 3.2 MB

Got: 4.2 MB Expected: ≤ 1 MB

~67 KB of savings available

111 third-party resources (16% of weight)

1 resources over 200KB

366 resources · 4.2 MiB · 111 third-party 3.2 MiB over 1MB target

Image 51% · 2.1 MiB

JavaScript 41% · 1.7 MiB

Font 4% · 163.7 KiB

Document 3% · 116.8 KiB

Other 1% · 29.3 KiB

CSS 0% · 20.1 KiB

~67.2 KiB of savings available

Remove unused JavaScript: 67.2 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

366 resources			4.2 MiB

A+

Third-Party Impact

16% third-party, 0 ms blocking

PASS

16% third-party, 0 ms blocking

Third-party code accounts for 16% of page weight (705.5 KiB of 4.2 MiB)

Third-party blocking time is low (0 ms)

84%

16%

First-party Third-party

A+

Text Compression

All text resources are compressed

PASS

All text resources are compressed

All text resources are properly compressed.

A+

Font Loading

4 fonts (164 KB)

PASS

4 fonts (164 KB)

4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

164 KB total

Render-blocking

of 4

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

inter_n5.d7101d5e168594... woff2 swap

Size 39 KB

Load time 55 ms

Start 818 ms

Risk FOUT — text flashes from fallback to web font

archivo_n5.272841b6d6b8... woff2 swap

Size 46 KB

Load time 61 ms

Start 818 ms

Risk FOUT — text flashes from fallback to web font

inter_n7.02711e6b374660... woff2 swap

Size 39 KB

Load time 87 ms

Start 963 ms

Risk FOUT — text flashes from fallback to web font

inter_n4.b2a3f24c19b4de... woff2 swap

Size 39 KB

Load time 38 ms

Start 1.6 s

Risk FOUT — text flashes from fallback to web font

Optimization checklist

Preload critical fonts (priority=high)
Use woff2 format for all fonts
Set font-display to swap, optional, or fallback
Subset large fonts (≤100 KB each)

A+

Resource Caching

All resources properly cached

PASS

All resources properly cached

No caching issues found

All static resources have appropriate caching headers.

A+

Critical Rendering Path

No render-blocking resources

PASS

No render-blocking resources

No render-blocking resources detected

A+

Resource Hints

No optimization needed

PASS

No optimization needed

No resource hint issues

A+

HTTP/3 (QUIC)

HTTP/3 advertised via Alt-Svc

PASS

HTTP/3 advertised via Alt-Svc

HTTP/3 (QUIC) is supported

First-load mobile users on cellular networks see meaningful latency improvements with HTTP/3. The QUIC transport collapses TLS + TCP handshakes into one and recovers faster from packet loss.

A+

Document Compression

Document response uses brotli

PASS

Document response uses brotli

Main HTML response uses brotli (Content-Encoding: br)

Brotli is the best text-compression algorithm for general use, ~20% smaller than gzip on average (40% on smaller files). Modern browsers all support it.

A+

Asset Compression

All 5 asset hosts use brotli

PASS

All 5 asset hosts use brotli

cdn.shopify.com serves assets with brotli (assets: 8)

Got: cdn.shopify.com (text/javascript)

js.smile.io serves assets with brotli (assets: 6)

Got: js.smile.io (text/javascript)

static.klaviyo.com serves assets with brotli (assets: 5)

Got: static.klaviyo.com (application/javascript)

cdn.jsdelivr.net serves assets with brotli (assets: 3)

Got: cdn.jsdelivr.net (text/css)

static-tracking.klaviyo.com serves assets with brotli (assets: 3)

Got: static-tracking.klaviyo.com (text/javascript)

A+

LCP Image Preload

LCP preload audit not available

PASS

LCP preload audit not available

LCP image preload audit not available for this scan

A+

Server-Timing Observability

18 Server-Timing entries advertised

PASS

18 Server-Timing entries advertised

Server-Timing header advertises 18 timing entries

A+

Server Response Intelligence

2 server-response signal(s) detected

PASS

2 server-response signal(s) detected

`Vary` header declared: accept-encoding

The page declares a `Vary` header, telling downstream caches which request headers the response varies on. Critical for content-negotiated responses (compression, language, cookies, device class).

`ETag` present -- conditional GET supported

A+

Green Hosting

Whether the site is served from green-energy infrastructure

PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Network Waterfall

366 requests over 4967ms

INFO

HTML JavaScript CSS Images Fonts XHR/Fetch Other

Real-User Performance (CrUX)

Field metrics from the Chrome User Experience Report

INFO

Chrome User Experience (CrUX)

Real-user metrics from the Chrome UX Report (2026-09-29 — 2026-10-26)

LCP (p75)

2293 ms

80% good

INP (p75)

142 ms

85% good

CLS (p75)

0.010

99% good

FCP (p75)

1928 ms

TTFB (p75)

918 ms

This origin passes Core Web Vitals assessment

Image Optimization

130 images, 1158 KB total, 823 KB wasted

INFO

Image Optimization Audit

Total Images

130

Total Size

1158 KB

Oversized

Wasted

823 KB

96 missing dimensions 92 missing lazy loading

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.