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https://firefox.com

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
86
GRADE
B
FIX
3
REVIEW
2
PASS
10
INFO
2

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

Mobile Desktop
62
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.
92
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.

3.78 s

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

4.41 s

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

530 ms

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

0.035

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

3.78 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.

5.36 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
17
10 PASS 2 REVIEW 3 FIX
D
Third-Party Impact
Action
100% third-party, 0 ms blocking
FIX
100% third-party, 0 ms blocking
Warning::
Third-party code accounts for 100% of page weight (505.3 KiB of 505.5 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
3311ms total JS execution
FIX
3311ms total JS execution
Warning::
https://www.firefox.com/en-US/: 1603ms CPU time
Warning::
Unattributable: 657ms CPU time
Warning::
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a4...: 551ms CPU time
Info::
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a4...: 200ms CPU time
Info::
https://www.firefox.com/media/js/firefox-cms-flare...: 158ms CPU time
Warning::
Third-party scripts: 3311ms (100% of total)

Main Thread Breakdown

Other 37% Script Evaluation 25% Style & Layout 19% Rendering 11% Script Parsing & Compilation 4%
ScriptTotalScriptingParse/CompileParty
https://www.firefox.com/en-US/1603ms26ms1ms3rd
Unattributable657ms36ms0ms3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js551ms462ms59ms3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js200ms162ms32ms3rd
https://www.firefox.com/media/js/firefox-cms-flare26.c214e922a79f.js158ms95ms20ms3rd
https://www.firefox.com/media/js/lib.244fb6035eee.js143ms16ms3ms3rd
F
HTTP Caching
Action
No cache headers
FIX
No cache headers
Warning::
No Cache-Control header found
Browsers will use heuristic caching, which can be unpredictable. Set explicit cache headers.

No Cache-Control header

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

B
Image Optimization
19 images, 0 KB saveable
REVIEW
19 images, 0 KB saveable
Info::
All images are well-optimized
19 images 113 KB
0 oversized -0 KB
19 legacy format
0 missing dimensions CLS risk
B
JS Bundles
14 scripts, 73 KB unused
REVIEW
14 scripts, 73 KB unused
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: 73 KB
73 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js99 KB45 KB (46%)✓3rd
https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js52 KB28 KB (54%)✓3rd
https://www.firefox.com/media/js/firefox-cms-flare26.c214e922a79f.js25 KB—✓3rd
https://www.firefox.com/media/js/sentry.2f57b70e06a9.js19 KB—✓3rd
https://www.firefox.com/media/js/lib.244fb6035eee.js6 KB—✓3rd
https://www.firefox.com/media/js/data.66a011d9be0e.js2 KB—✓3rd
https://www.firefox.com/media/js/gtm-snippet.75f2d1f2194b.js1 KB—✓3rd
https://www.firefox.com/media/js/ui-tour-buttons.5f82dc085f31.js1 KB—✓3rd
https://www.firefox.com/media/js/flare-navigation.17c4a3a73443.js9 KB—✓3rd
https://www.firefox.com/media/js/flare-lang-switcher.90adb422979f.js1 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

A+
Page Weight Budget
505 KB transferred, 43 requests
PASS
505 KB transferred, 43 requests
Info::
Page weighs 1.4 MB (505 KB transferred)
Info::
43 HTTP requests
Info::
Estimated 0.10 g CO2 per page load
505 KB / 2.4 MB budget
505 KB transferred
43 requests
0.10 g CO2 per page load
JavaScript 224.6 KiB 44%
Images 112.6 KiB 22%
Fonts 101.3 KiB 20%
CSS 40.6 KiB 8%
HTML 15.2 KiB 3%
Other 8.7 KiB 2%
Other 2.5 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
2 fonts (101 KB)
PASS
2 fonts (101 KB)
Info::
2 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

2

101 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 1.0 s 2.0 s 3.0 s 4.0 s FCP 3.8 s LCP 4.4 shttps://www.firefox.com/media/fonts/mozilla-headline/MozillaHeadline-Variable.19ade5d17bd1.woff2MozillaHeadline-Variabl... https://www.firefox.com/media/fonts/mozilla-headline/MozillaHeadline-Variable.19ade5d17bd1.woff2 — 68.3 KiB — 10 ms — font-display: swaphttps://www.firefox.com/media/fonts/mozilla-text/MozillaText-Variable.fc7317808d75.woff2MozillaText-Variable.fc... https://www.firefox.com/media/fonts/mozilla-text/MozillaText-Variable.fc7317808d75.woff2 — 33.0 KiB — 8 ms — font-display: swap
MozillaHeadline-Variabl... woff2 swap
Size 68 KB
Load time 10 ms
Start 938 ms
Risk FOUT — text flashes from fallback to web font
MozillaText-Variable.fc... woff2 swap
Size 33 KB
Load time 8 ms
Start 938 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
Page Weight Inventory
43 resources · 505 KB · 73 KB savings available
PASS
43 resources · 505 KB · 73 KB savings available
Info::
Within 1MB page-weight target
Got: 505 KB
Info::
~73 KB of savings available
Warning::
42 third-party resources (100% of weight)
43 resources · 505.5 KiB · 42 third-party Within 1MB page-weight target
JavaScript 44% · 224.6 KiB
Image 24% · 120.8 KiB
Font 20% · 101.3 KiB
CSS 8% · 40.6 KiB
Document 3% · 15.8 KiB
Other 0% · 2.5 KiB

~73.2 KiB of savings available

Remove unused JavaScript: 73.2 KiB
A+
Render-Blocking Resources
No render-blocking resources detected
PASS
No render-blocking resources detected
Info::
No render-blocking resources detected in <head>
A+
Third-Party Resources
No third-party resources detected
PASS
No third-party resources detected
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Google Cloud

Network Waterfall
43 requests over 1305ms
INFO
0 ms 1.0 s 2.0 s 3.0 s 4.0 s FCP 3.8 s LCP 4.4 shttps://firefox.com// https://firefox.com/ — 302 — 157 B — 571 ms — h2https://www.firefox.com/www.firefox.com/ https://www.firefox.com/ — 302 — 392 B — 15 ms — h2https://www.firefox.com/en-US/www.firefox.com/en-US/ https://www.firefox.com/en-US/ — 200 — 15.2 KiB — 7 ms — h2https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.jstranscend-cdn.com/cm/d556c3a1-e57c-... https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js — 200 — 52.2 KiB — 67 ms — h3https://www.firefox.com/media/css/flare26.b59da170eadc.csswww.firefox.com/media/css/flare26.b... https://www.firefox.com/media/css/flare26.b59da170eadc.css — 200 — 32.8 KiB — 34 ms — h2https://www.firefox.com/media/js/site.4dabcff0fc9f.jswww.firefox.com/media/js/site.4dabc... https://www.firefox.com/media/js/site.4dabcff0fc9f.js — 200 — 2.4 KiB — 35 ms — h2https://www.firefox.com/media/js/gtm-snippet.75f2d1f2194b.jswww.firefox.com/media/js/gtm-snippe... https://www.firefox.com/media/js/gtm-snippet.75f2d1f2194b.js — 200 — 1.3 KiB — 44 ms — h2https://www.firefox.com/media/js/sentry.2f57b70e06a9.jswww.firefox.com/media/js/sentry.2f5... https://www.firefox.com/media/js/sentry.2f57b70e06a9.js — 200 — 19.4 KiB — 39 ms — h2https://www.firefox.com/media/js/lib.244fb6035eee.jswww.firefox.com/media/js/lib.244fb6... https://www.firefox.com/media/js/lib.244fb6035eee.js — 200 — 5.9 KiB — 46 ms — h2https://www.firefox.com/media/js/data.66a011d9be0e.jswww.firefox.com/media/js/data.66a01... https://www.firefox.com/media/js/data.66a011d9be0e.js — 200 — 2.2 KiB — 8 ms — h2https://www.firefox.com/media/js/firefox-cms-flare26.c214e922a79f.jswww.firefox.com/media/js/firefox-cm... https://www.firefox.com/media/js/firefox-cms-flare26.c214e922a79f.js — 200 — 24.8 KiB — 15 ms — h2https://www.firefox.com/media/js/ui-tour-buttons.5f82dc085f31.jswww.firefox.com/media/js/ui-tour-bu... https://www.firefox.com/media/js/ui-tour-buttons.5f82dc085f31.js — 200 — 1014 B — 9 ms — h2https://www.firefox.com/media/js/flare-navigation.17c4a3a73443.jswww.firefox.com/media/js/flare-navi... https://www.firefox.com/media/js/flare-navigation.17c4a3a73443.js — 200 — 9.4 KiB — 4 ms — h2https://www.firefox.com/media/js/flare-lang-switcher.90adb422979f.jswww.firefox.com/media/js/flare-lang... https://www.firefox.com/media/js/flare-lang-switcher.90adb422979f.js — 200 — 790 B — 7 ms — h2https://www.firefox.com/media/js/consent-banner.35e30dbc9f8f.jswww.firefox.com/media/js/consent-ba... https://www.firefox.com/media/js/consent-banner.35e30dbc9f8f.js — 200 — 2.4 KiB — 5 ms — h2https://www.firefox.com/media/js/stub-attribution.502fd79d417f.jswww.firefox.com/media/js/stub-attri... https://www.firefox.com/media/js/stub-attribution.502fd79d417f.js — 200 — 2.9 KiB — 15 ms — h2https://www.firefox.com/media/js/download_as_default.740bb0ac58b9.jswww.firefox.com/media/js/download_a... https://www.firefox.com/media/js/download_as_default.740bb0ac58b9.js — 200 — 1.5 KiB — 15 ms — h2https://www.firefox.com/media/img/logos/firefox/logo-word-hor-2026.svgwww.firefox.com/media/img/logos/fir... https://www.firefox.com/media/img/logos/firefox/logo-word-hor-2026.svg — 200 — 5.4 KiB — 16 ms — h2https://www.firefox.com/media/img/l10n/en-US/firefox/ios/btn-app-store.1cfd5dba4a92.svgwww.firefox.com/media/img/l10n/en-U... https://www.firefox.com/media/img/l10n/en-US/firefox/ios/btn-app-store.1cfd5dba4a92.svg — 200 — 4.7 KiB — 16 ms — h2https://www.firefox.com/media/img/l10n/en-US/firefox/android/btn-google-play-high-res.87d9720bbc8b.pngwww.firefox.com/media/img/l10n/en-U... https://www.firefox.com/media/img/l10n/en-US/firefox/android/btn-google-play-high-res.87d9720bbc8b.png — 200 — 4.8 KiB — 17 ms — h2https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.jstranscend-cdn.com/cm/d556c3a1-e57c-... https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js — 200 — 98.6 KiB — 38 ms — h3https://www.firefox.com/media/css/flare26_base.6222ecc62b3a.csswww.firefox.com/media/css/flare26_b... https://www.firefox.com/media/css/flare26_base.6222ecc62b3a.css — 200 — 3.6 KiB — 15 ms — h2https://www.firefox.com/media/img/logos/firefox/logo-word-hor-white-2026.38b0d9aa301a.svgwww.firefox.com/media/img/logos/fir... https://www.firefox.com/media/img/logos/firefox/logo-word-hor-white-2026.38b0d9aa301a.svg — 200 — 5.4 KiB — 9 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/downloads/downloads-16.20e252d0a92b.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/downloads/downloads-16.20e252d0a92b.svg — 200 — 745 B — 12 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/app-menu/app-menu-16.db78d62c836a.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/app-menu/app-menu-16.db78d62c836a.svg — 200 — 518 B — 14 ms — h2https://www.firefox.com/media/img/firefox/flare/kit-dive.26257f27e8a0.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/kit-dive.26257f27e8a0.svg — 200 — 6.1 KiB — 23 ms — h2https://www.firefox.com/media/img/firefox/flare/sitting-kit-2.f9dedcdd542b.pngwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/sitting-kit-2.f9dedcdd542b.png — 200 — 63.8 KiB — 26 ms — h2https://www.firefox.com/media/img/firefox/flare/kit-tail-2.1608e2bf46c5.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/kit-tail-2.1608e2bf46c5.svg — 200 — 7.6 KiB — 6 ms — h2https://www.firefox.com/media/img/firefox/flare/fox-brand-curious.3ea99c60c166.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/fox-brand-curious.3ea99c60c166.svg — 200 — 2.9 KiB — 6 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/search/search-16.33cf8483a28f.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/search/search-16.33cf8483a28f.svg — 200 — 754 B — 9 ms — h2
0 ms 1.0 s 2.0 s 3.0 s 4.0 s FCP 3.8 s LCP 4.4 shttps://firefox.com// https://firefox.com/ — 302 — 157 B — 571 ms — h2https://www.firefox.com/www.firefox.com/ https://www.firefox.com/ — 302 — 392 B — 15 ms — h2https://www.firefox.com/en-US/www.firefox.com/en-US/ https://www.firefox.com/en-US/ — 200 — 15.2 KiB — 7 ms — h2https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.jstranscend-cdn.com/cm/d556c3a1-e57c-... https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js — 200 — 52.2 KiB — 67 ms — h3https://www.firefox.com/media/css/flare26.b59da170eadc.csswww.firefox.com/media/css/flare26.b... https://www.firefox.com/media/css/flare26.b59da170eadc.css — 200 — 32.8 KiB — 34 ms — h2https://www.firefox.com/media/js/site.4dabcff0fc9f.jswww.firefox.com/media/js/site.4dabc... https://www.firefox.com/media/js/site.4dabcff0fc9f.js — 200 — 2.4 KiB — 35 ms — h2https://www.firefox.com/media/js/gtm-snippet.75f2d1f2194b.jswww.firefox.com/media/js/gtm-snippe... https://www.firefox.com/media/js/gtm-snippet.75f2d1f2194b.js — 200 — 1.3 KiB — 44 ms — h2https://www.firefox.com/media/js/sentry.2f57b70e06a9.jswww.firefox.com/media/js/sentry.2f5... https://www.firefox.com/media/js/sentry.2f57b70e06a9.js — 200 — 19.4 KiB — 39 ms — h2https://www.firefox.com/media/js/lib.244fb6035eee.jswww.firefox.com/media/js/lib.244fb6... https://www.firefox.com/media/js/lib.244fb6035eee.js — 200 — 5.9 KiB — 46 ms — h2https://www.firefox.com/media/js/data.66a011d9be0e.jswww.firefox.com/media/js/data.66a01... https://www.firefox.com/media/js/data.66a011d9be0e.js — 200 — 2.2 KiB — 8 ms — h2https://www.firefox.com/media/js/firefox-cms-flare26.c214e922a79f.jswww.firefox.com/media/js/firefox-cm... https://www.firefox.com/media/js/firefox-cms-flare26.c214e922a79f.js — 200 — 24.8 KiB — 15 ms — h2https://www.firefox.com/media/js/ui-tour-buttons.5f82dc085f31.jswww.firefox.com/media/js/ui-tour-bu... https://www.firefox.com/media/js/ui-tour-buttons.5f82dc085f31.js — 200 — 1014 B — 9 ms — h2https://www.firefox.com/media/js/flare-navigation.17c4a3a73443.jswww.firefox.com/media/js/flare-navi... https://www.firefox.com/media/js/flare-navigation.17c4a3a73443.js — 200 — 9.4 KiB — 4 ms — h2https://www.firefox.com/media/js/flare-lang-switcher.90adb422979f.jswww.firefox.com/media/js/flare-lang... https://www.firefox.com/media/js/flare-lang-switcher.90adb422979f.js — 200 — 790 B — 7 ms — h2https://www.firefox.com/media/js/consent-banner.35e30dbc9f8f.jswww.firefox.com/media/js/consent-ba... https://www.firefox.com/media/js/consent-banner.35e30dbc9f8f.js — 200 — 2.4 KiB — 5 ms — h2https://www.firefox.com/media/js/stub-attribution.502fd79d417f.jswww.firefox.com/media/js/stub-attri... https://www.firefox.com/media/js/stub-attribution.502fd79d417f.js — 200 — 2.9 KiB — 15 ms — h2https://www.firefox.com/media/js/download_as_default.740bb0ac58b9.jswww.firefox.com/media/js/download_a... https://www.firefox.com/media/js/download_as_default.740bb0ac58b9.js — 200 — 1.5 KiB — 15 ms — h2https://www.firefox.com/media/img/logos/firefox/logo-word-hor-2026.svgwww.firefox.com/media/img/logos/fir... https://www.firefox.com/media/img/logos/firefox/logo-word-hor-2026.svg — 200 — 5.4 KiB — 16 ms — h2https://www.firefox.com/media/img/l10n/en-US/firefox/ios/btn-app-store.1cfd5dba4a92.svgwww.firefox.com/media/img/l10n/en-U... https://www.firefox.com/media/img/l10n/en-US/firefox/ios/btn-app-store.1cfd5dba4a92.svg — 200 — 4.7 KiB — 16 ms — h2https://www.firefox.com/media/img/l10n/en-US/firefox/android/btn-google-play-high-res.87d9720bbc8b.pngwww.firefox.com/media/img/l10n/en-U... https://www.firefox.com/media/img/l10n/en-US/firefox/android/btn-google-play-high-res.87d9720bbc8b.png — 200 — 4.8 KiB — 17 ms — h2https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.jstranscend-cdn.com/cm/d556c3a1-e57c-... https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js — 200 — 98.6 KiB — 38 ms — h3https://www.firefox.com/media/css/flare26_base.6222ecc62b3a.csswww.firefox.com/media/css/flare26_b... https://www.firefox.com/media/css/flare26_base.6222ecc62b3a.css — 200 — 3.6 KiB — 15 ms — h2https://www.firefox.com/media/img/logos/firefox/logo-word-hor-white-2026.38b0d9aa301a.svgwww.firefox.com/media/img/logos/fir... https://www.firefox.com/media/img/logos/firefox/logo-word-hor-white-2026.38b0d9aa301a.svg — 200 — 5.4 KiB — 9 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/downloads/downloads-16.20e252d0a92b.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/downloads/downloads-16.20e252d0a92b.svg — 200 — 745 B — 12 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/app-menu/app-menu-16.db78d62c836a.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/app-menu/app-menu-16.db78d62c836a.svg — 200 — 518 B — 14 ms — h2https://www.firefox.com/media/img/firefox/flare/kit-dive.26257f27e8a0.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/kit-dive.26257f27e8a0.svg — 200 — 6.1 KiB — 23 ms — h2https://www.firefox.com/media/img/firefox/flare/sitting-kit-2.f9dedcdd542b.pngwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/sitting-kit-2.f9dedcdd542b.png — 200 — 63.8 KiB — 26 ms — h2https://www.firefox.com/media/img/firefox/flare/kit-tail-2.1608e2bf46c5.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/kit-tail-2.1608e2bf46c5.svg — 200 — 7.6 KiB — 6 ms — h2https://www.firefox.com/media/img/firefox/flare/fox-brand-curious.3ea99c60c166.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/fox-brand-curious.3ea99c60c166.svg — 200 — 2.9 KiB — 6 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/search/search-16.33cf8483a28f.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/search/search-16.33cf8483a28f.svg — 200 — 754 B — 9 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/profile/palette-16.028234691e78.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/profile/palette-16.028234691e78.svg — 200 — 1.1 KiB — 8 ms — h2https://www.firefox.com/media/cms/images/Shield_41DIZ0q.width-400.svgwww.firefox.com/media/cms/images/Sh... https://www.firefox.com/media/cms/images/Shield_41DIZ0q.width-400.svg — 200 — 2.1 KiB — 6 ms — h2https://www.firefox.com/media/cms/images/Cursor_HIkIYqM.width-400.svgwww.firefox.com/media/cms/images/Cu... https://www.firefox.com/media/cms/images/Cursor_HIkIYqM.width-400.svg — 200 — 1.4 KiB — 9 ms — h2https://www.firefox.com/media/cms/images/Toggle_DNTkMhH.width-400.svgwww.firefox.com/media/cms/images/To... https://www.firefox.com/media/cms/images/Toggle_DNTkMhH.width-400.svg — 200 — 1.5 KiB — 12 ms — h2https://www.firefox.com/media/cms/images/Bolt_GL1BlXf.width-400.svgwww.firefox.com/media/cms/images/Bo... https://www.firefox.com/media/cms/images/Bolt_GL1BlXf.width-400.svg — 200 — 1.4 KiB — 14 ms — h2https://www.firefox.com/media/fonts/mozilla-headline/MozillaHeadline-Variable.19ade5d17bd1.woff2www.firefox.com/media/fonts/mozilla... https://www.firefox.com/media/fonts/mozilla-headline/MozillaHeadline-Variable.19ade5d17bd1.woff2 — 200 — 68.3 KiB — 10 ms — h2https://www.firefox.com/media/fonts/mozilla-text/MozillaText-Variable.fc7317808d75.woff2www.firefox.com/media/fonts/mozilla... https://www.firefox.com/media/fonts/mozilla-text/MozillaText-Variable.fc7317808d75.woff2 — 200 — 33.0 KiB — 8 ms — h2https://www.firefox.com/media/img/icons/external.e2b4246cf764.svgwww.firefox.com/media/img/icons/ext... https://www.firefox.com/media/img/icons/external.e2b4246cf764.svg — 200 — 744 B — 7 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/globe/globe-16.74af97ffa793.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/globe/globe-16.74af97ffa793.svg — 200 — 877 B — 7 ms — h2https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/arrows-and-chevrons/chevron-down-16.e2f145363ee8.svgwww.firefox.com/media/img/firefox/f... https://www.firefox.com/media/img/firefox/flare/2026/icons/desktop-16/arrows-and-chevrons/chevron-down-16.e2f145363ee8.svg — 200 — 733 B — 7 ms — h2https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/cm.csstranscend-cdn.com/cm/d556c3a1-e57c-... https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/cm.css — 200 — 4.1 KiB — 20 ms — h3https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/translations/en.jsontranscend-cdn.com/cm/d556c3a1-e57c-... https://transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/translations/en.json — 200 — 2.5 KiB — 21 ms — h3https://www.firefox.com/media/img/favicons/firefox/browser/favicon.f093404c0135.icowww.firefox.com/media/img/favicons/... https://www.firefox.com/media/img/favicons/firefox/browser/favicon.f093404c0135.ico — 200 — 8.2 KiB — 8 ms — h2
HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
INFO
100% of JavaScript execution is third-party
First-party Third-party 3311ms · 197KB · €36/mo
www.firefox.com
Other
Costly
Execution 1603ms
Transfer 15 KB
Monthly Cost €17/mo
Unattributable
Other
Costly
Execution 657ms
Transfer 0 KB
Monthly Cost €7/mo
transcend-cdn.com
Other
Costly
Execution 551ms
Transfer 99 KB
Unused 46%
Monthly Cost €6/mo
transcend-cdn.com
Other
Costly
Execution 200ms
Transfer 52 KB
Unused 54%
Monthly Cost €2/mo
www.firefox.com
Other
Optional
Execution 158ms
Transfer 25 KB
Monthly Cost €2/mo
www.firefox.com
Other
Optional
Execution 143ms
Transfer 6 KB
Monthly Cost €2/mo

These scripts may cost more than they're worth

  • www.firefox.com adds 1603ms and costs ~€17/month
  • Unattributable adds 657ms and costs ~€7/month
  • transcend-cdn.com adds 551ms and costs ~€6/month
  • transcend-cdn.com adds 200ms and costs ~€2/month

100% 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

www.firefox.com takes 1603ms 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

Unattributable takes 657ms 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 551ms 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 200ms 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.

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