Skip to content
https://www.mozilla.org

Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
83
GRADE
B
FIX
1
REVIEW
4
PASS
7
INFO
2

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

Mobile Desktop
51
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
100
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.

2.33 s

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

2.85 s

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

679 ms

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

0.948

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

2.83 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.

6.45 s

Page Load Progression

488 ms
975 ms
1.5 s
1.9 s
2.4 s
2.9 s
3.4 s
3.9 s
Checks
14
7 PASS 4 REVIEW 1 FIX
D
JS Execution Cost
Action
2461ms total JS execution
FIX
2461ms total JS execution
Warning::
Unattributable: 593ms CPU time
Warning::
https://www.mozilla.org/en-US/: 562ms CPU time
Warning::
https://www.googletagmanager.com/gtag/js?id=G-MQ77...: 473ms CPU time
Warning::
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a4...: 345ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-MW3...: 241ms CPU time
Warning::
Third-party scripts: 1819ms (74% of total)

Main Thread Breakdown

Script Evaluation 42% Other 26% Style & Layout 14% Script Parsing & Compilation 8% Parse HTML & CSS 3% Garbage Collection 3%
ScriptTotalScriptingParse/CompileParty
Unattributable593ms21ms0ms3rd
https://www.mozilla.org/en-US/562ms20ms1ms1st
https://www.googletagmanager.com/gtag/js?id=G-MQ7767QQQW&cx=c&gtm=4e6411473ms366ms71ms3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js345ms264ms53ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MW3R8V&l=dataLayer241ms179ms51ms3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js166ms137ms18ms3rd
https://www.mozilla.org/media/js/sentry.31edfa94a7f6.js81ms37ms8ms1st
B
Third-Party Impact
59% third-party, 0 ms blocking
REVIEW
59% third-party, 0 ms blocking
Warning::
Third-party code accounts for 59% of page weight (457.8 KiB of 769.9 KiB)
Info::
Third-party blocking time is low (0 ms)
41%
59%
First-party Third-party
B
Image Optimization
22 images, 0 KB saveable
REVIEW
22 images, 0 KB saveable
Info::
All images are well-optimized
22 images 114 KB
0 oversized -0 KB
21 legacy format
0 missing dimensions CLS risk
C
JS Bundles
Action
15 scripts, 202 KB unused
REVIEW
15 scripts, 202 KB unused
Warning::
https://www.googletagmanager.com/gtag/js?id=G-MQ77...: 70 KB unused (40%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-MW3...: 59 KB unused (48%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a4...: 45 KB unused (46%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a4...: 28 KB unused (54%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 202 KB
202 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtag/js?id=G-MQ7767QQQW&cx=c&gtm=4e6411175 KB70 KB (40%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MW3R8V&l=dataLayer125 KB59 KB (48%)✓3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js98 KB45 KB (46%)✓3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js52 KB28 KB (54%)✓3rd
https://www.mozilla.org/media/js/fxa.f30434397531.js3 KB—✓1st
https://www.mozilla.org/media/js/lib.c244ff81b28a.js6 KB—✓1st
https://www.mozilla.org/media/js/sentry.31edfa94a7f6.js19 KB—✓1st
https://www.mozilla.org/media/js/data.a85f0425619e.js3 KB—✓1st
https://www.mozilla.org/media/js/m24-ui.71f62c655696.js4 KB—✓1st
https://www.mozilla.org/media/js/stub-attribution.819aeb6b157b.js3 KB—✓1st

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

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A
Page Weight Budget
770 KB transferred, 52 requests
PASS
770 KB transferred, 52 requests
Info::
Page weighs 2.0 MB (770 KB transferred)
Info::
52 HTTP requests
Info::
Estimated 0.16 g CO2 per page load
770 KB / 2.4 MB budget
770 KB transferred
52 requests
0.16 g CO2 per page load
JavaScript 497.2 KiB 65%
Images 114.2 KiB 15%
Fonts 107.1 KiB 14%
CSS 25.6 KiB 3%
HTML 21.3 KiB 3%
Other 3.0 KiB 0%
Other 1.4 KiB 0%
0 2.4 MB 4.9 MB
Under budget
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
4 fonts (107 KB)
PASS
4 fonts (107 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

107 KB total

Render-blocking

0

of 4

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 2.3 s LCP 2.8 shttps://www.mozilla.org/media/protocol/fonts/mozilla-text/MozillaText-SemiBold.b126cc23eddf.woff2MozillaText-SemiBold.b1... https://www.mozilla.org/media/protocol/fonts/mozilla-text/MozillaText-SemiBold.b126cc23eddf.woff2 — 26.1 KiB — 0 ms — font-display: swaphttps://www.mozilla.org/media/protocol/fonts/mozilla-headline/MozillaHeadline-SemiBold.bccc6c46c123.woff2MozillaHeadline-SemiBol... https://www.mozilla.org/media/protocol/fonts/mozilla-headline/MozillaHeadline-SemiBold.bccc6c46c123.woff2 — 28.5 KiB — 0 ms — font-display: swaphttps://www.mozilla.org/media/protocol/fonts/mozilla-text/MozillaText-Regular.71c103450d6d.woff2MozillaText-Regular.71c... https://www.mozilla.org/media/protocol/fonts/mozilla-text/MozillaText-Regular.71c103450d6d.woff2 — 26.2 KiB — 0 ms — font-display: swaphttps://www.mozilla.org/media/protocol/fonts/mozilla-text/MozillaText-Bold.4af7ce689fd6.woff2MozillaText-Bold.4af7ce... https://www.mozilla.org/media/protocol/fonts/mozilla-text/MozillaText-Bold.4af7ce689fd6.woff2 — 26.3 KiB — 0 ms — font-display: swap
MozillaText-SemiBold.b1... woff2 swap
Size 26 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
MozillaHeadline-SemiBol... woff2 swap
Size 29 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
MozillaText-Regular.71c... woff2 swap
Size 26 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
MozillaText-Bold.4af7ce... woff2 swap
Size 26 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
A+
HTTP Caching
max-age=600 (10 minutes)
PASS
max-age=600 (10 minutes)
Info::
Cache-Control header is set
Got: max-age=600
Info::
Effective TTL: 10 minutes (max-age=600)
Info::
ETag present — enables conditional (304) responses
Cache-Control

max-age=600

DirectiveValueMeaning
max-age600Cache for 10 minutes
Effective TTL: 600 seconds
Network Waterfall
52 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
74% of JavaScript execution is third-party
First-party Third-party 1819ms · 451KB · €20/mo
Unattributable
Other
Costly
Execution 593ms
Transfer 0 KB
Monthly Cost €6/mo
Google Tag Manager
Tag Manager
Costly
Execution 473ms
Transfer 175 KB
Unused 40%
Monthly Cost €5/mo
transcend-cdn.com
Other
Costly
Execution 345ms
Transfer 98 KB
Unused 46%
Monthly Cost €4/mo
Google Tag Manager
Tag Manager
Costly
Execution 241ms
Transfer 125 KB
Unused 48%
Monthly Cost €3/mo
transcend-cdn.com
Other
Optional
Execution 166ms
Transfer 52 KB
Unused 54%
Monthly Cost €2/mo

These scripts may cost more than they're worth

  • Unattributable adds 593ms and costs ~€6/month
  • Google Tag Manager adds 473ms and costs ~€5/month
  • transcend-cdn.com adds 345ms and costs ~€4/month
  • Google Tag Manager adds 241ms and costs ~€3/month

74% 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

Unattributable takes 593ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 473ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

transcend-cdn.com takes 345ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

Google Tag Manager takes 241ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters

This script has high main-thread execution time — optimize hot paths or defer.

Source: web.dev

54% of transcend-cdn.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.

Send Feedback