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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
74
GRADE
C
FIX
4
REVIEW
3
PASS
5
INFO
2

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

Mobile Desktop
81
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
97
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
96
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
100
SEO Measures basic SEO optimizations: meta tags, crawlability, link text, and mobile friendliness.

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

1.31 s

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

2.43 s

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

60 ms

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

0.021

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

1.86 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.

2.63 s

Page Load Progression

375 ms
750 ms
1.1 s
1.5 s
1.9 s
2.2 s
2.6 s
3.0 s
Checks
14
5 PASS 3 REVIEW 4 FIX
F
Page Weight Budget
Action
3.3 MB transferred, 68 requests
FIX
3.3 MB transferred, 68 requests
Warning::
Page weighs 7.1 MB (3.3 MB transferred)
Warning::
Images are 1.6 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 1.6 MB
Warning::
JavaScript is 1.4 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.4 MB
Info::
68 HTTP requests
Info::
Estimated 0.70 g CO2 per page load
3.3 MB / 2.4 MB budget
3.3 MB transferred
68 requests
0.70 g CO2 per page load
Images 1.6 MiB 49%
JavaScript 1.4 MiB 41%
HTML 128.0 KiB 4%
Fonts 83.9 KiB 2%
Other 62.7 KiB 2%
CSS 49.6 KiB 1%
Other 1.8 KiB 0%
Other 883 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

D
Third-Party Impact
Action
94% third-party, 0 ms blocking
FIX
94% third-party, 0 ms blocking
Warning::
Third-party code accounts for 94% of page weight (3.1 MiB of 3.3 MiB)
Info::
Third-party blocking time is low (0 ms)
94%
First-party Third-party
F
JS Bundles
Action
20 scripts, 593 KB unused
FIX
20 scripts, 593 KB unused
Warning::
https://web-assets.strava.com/assets/landing-pages...: 256 KB unused (58%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://web-assets.strava.com/assets/landing-pages...: 72 KB unused (81%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-TP8...: 71 KB unused (43%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=DC-150...: 62 KB unused (48%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-ESZ0...: 62 KB unused (36%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 593 KB
593 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/pages/_app-090d844577d2f000.js440 KB256 KB (58%)✓3rd
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/59947-2e0be482d37a1813.js91 KB72 KB (81%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-TP845S&l=googleTagManagerDataLayer165 KB71 KB (43%)✓3rd
https://www.googletagmanager.com/gtag/js?id=DC-15023759&l=googleTagManagerDataLayer&cx=c&gtm=4e6460h1129 KB62 KB (48%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-ESZ0QKJW56&l=googleTagManagerDataLayer&cx=c&gtm=4e6460h1174 KB62 KB (36%)✓3rd
https://consent.cookiebot.com/e47bebbc-d5c7-470a-a8f6-6d858aa50ff4/cc.js?renew=false&referer=www.strava.com&dnt=false&init=false&culture=en&georegions=%5B%7B%22r%22%3A%22US%2CAU%2CNZ%22%2C%22i%22%3A%2229065233-759b-47fb-b38d-6dc38804c519%22%7D%5D112 KB26 KB (23%)✓3rd
https://consent.cookiebot.com/uc.js36 KB22 KB (63%)✓3rd
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/main-6f5274bcc70697b8.js39 KB21 KB (54%)✓3rd
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/54780-b89ac63af46500f9.js22 KB—✓3rd
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/4672-6ba4c22895e35c25.js5 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

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

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

D
HTTP Caching
Action
no-store (uncacheable)
FIX
no-store (uncacheable)
Info::
Cache-Control: no-store prevents all caching
Intentional for dynamic content, but increases server load for every page view.
Got: private, no-cache, no-store, max-age=0, must-revalidate
Info::
ETag present — enables conditional (304) responses
Cache-Control

private, no-cache, no-store, max-age=0, must-revalidate

DirectiveValueMeaning
private—Only browser cache, not CDN/proxy
no-cache—Cache but always revalidate first
no-store—Never cache this response
max-age0Cache for 0 seconds
must-revalidate—Must recheck with server after expiry
C
Image Optimization
Action
29 images, 0 KB saveable
REVIEW
29 images, 0 KB saveable
Warning::
https://web-assets.strava.com/assets/landing-pages... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://web-assets.strava.com/assets/landing-pages... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
29 images 1.6 MB
0 oversized -0 KB
20 legacy format
2 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

B
JS Execution Cost
693ms total JS execution
REVIEW
693ms total JS execution
Info::
https://web-assets.strava.com/assets/landing-pages...: 182ms CPU time
Info::
https://web-assets.strava.com/assets/landing-pages...: 117ms CPU time
Info::
Unattributable: 111ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=DC-150...: 82ms CPU time
Info::
https://consent.cookiebot.com/e47bebbc-d5c7-470a-a...: 77ms CPU time
Warning::
Third-party scripts: 628ms (91% of total)

Main Thread Breakdown

Script Evaluation 61% Other 14% Script Parsing & Compilation 13% Style & Layout 5% Parse HTML & CSS 5%
ScriptTotalScriptingParse/CompileParty
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/pages/_app-090d844577d2f000.js182ms138ms37ms3rd
https://web-assets.strava.com/assets/landing-pages/_next/static/chunks/framework-7f9d59fd7074d9f7.js117ms109ms4ms3rd
Unattributable111ms8ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=DC-15023759&l=googleTagManagerDataLayer&cx=c&gtm=4e6460h182ms64ms9ms3rd
https://consent.cookiebot.com/e47bebbc-d5c7-470a-a8f6-6d858aa50ff4/cc.js?renew=false&referer=www.strava.com&dnt=false&init=false&culture=en&georegions=%5B%7B%22r%22%3A%22US%2CAU%2CNZ%22%2C%22i%22%3A%2229065233-759b-47fb-b38d-6dc38804c519%22%7D%5D77ms34ms9ms3rd
https://www.strava.com/65ms3ms0ms1st
https://www.googletagmanager.com/gtag/js?id=G-ESZ0QKJW56&l=googleTagManagerDataLayer&cx=c&gtm=4e6460h158ms45ms13ms3rd
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Text Compression
All text resources are compressed
PASS
All text resources are compressed
Info::
All text resources are compressed
All text resources are properly compressed.
A+
Font Loading
2 fonts (84 KB)
PASS
2 fonts (84 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

84 KB total

Render-blocking

0

of 2

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s 1.5 s 2.0 s 2.5 s FCP 1.3 s LCP 2.4 shttps://strava-web-assets.s3.amazonaws.com/assets/fonts/Boathouse/Static/Boathouse-Regular.woff2Boathouse-Regular.woff2 https://strava-web-assets.s3.amazonaws.com/assets/fonts/Boathouse/Static/Boathouse-Regular.woff2 — 41.8 KiB — 0 ms — font-display: swaphttps://strava-web-assets.s3.amazonaws.com/assets/fonts/Boathouse/Static/Boathouse-Medium.woff2Boathouse-Medium.woff2 https://strava-web-assets.s3.amazonaws.com/assets/fonts/Boathouse/Static/Boathouse-Medium.woff2 — 42.1 KiB — 0 ms — font-display: swap
Boathouse-Regular.woff2 woff2 swap
Size 42 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Boathouse-Medium.woff2 woff2 swap
Size 42 KB
Load time 0 ms
Start 0 ms
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
Info::
No caching issues found
All static resources have appropriate caching headers.
A+
Critical Rendering Path
No render-blocking resources
PASS
No render-blocking resources
Info::
No render-blocking resources detected
A+
Resource Hints
No optimization needed
PASS
No optimization needed
Info::
No resource hint issues
Network Waterfall
68 requests over 0ms
INFO

Performance analysis not available for this result.

Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
91% of JavaScript execution is third-party
First-party Third-party 628ms · 900KB · €10/mo
web-assets.strava.com
Other
Optional
Execution 182ms
Transfer 440 KB
Unused 58%
Monthly Cost €3/mo
web-assets.strava.com
Other
Optional
Execution 117ms
Transfer 45 KB
Monthly Cost €2/mo
Unattributable
Other
Optional
Execution 111ms
Transfer 0 KB
Monthly Cost €2/mo
Google Tag Manager
Tag Manager
Optional
Execution 82ms
Transfer 129 KB
Unused 48%
Monthly Cost €1/mo
consent.cookiebot.com
Other
Optional
Execution 77ms
Transfer 112 KB
Unused 23%
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 58ms
Transfer 174 KB
Unused 36%
Monthly Cost €1/mo

91% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.

Why this matters

When third-party JS execution time exceeds your own, performance gains from frontend work are capped by code you don't own.

Learn more ▾

Every millisecond of third-party JS competes with your own for main-thread time. If their share is bigger than yours, optimization on your code base barely moves the needle. Audit, defer, or remove third-parties before further frontend optimization. Use Lighthouse's third-party audit to identify the worst offenders.

Source: web.dev

58% of web-assets.strava.com's code is unused. The script may be loading features you don't use.

Why this matters

Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.

Source: web.dev

How third-party costs are calculated

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

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