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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
86
GRADE
B
FIX
0
REVIEW
5
PASS
7
INFO
2

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

Mobile Desktop
95
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
92
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
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.

1.02 s

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

1.28 s

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

44 ms

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

0.004

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

1.02 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.

2.11 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
7 PASS 5 REVIEW
C
Page Weight Budget
Action
1.7 MB transferred, 59 requests
REVIEW
1.7 MB transferred, 59 requests
Info::
Page weighs 3.3 MB (1.7 MB transferred)
Warning::
JavaScript is 696 KB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 696 KB
Info::
Fonts are 398 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 398 KB
Info::
59 HTTP requests
Info::
Estimated 0.35 g CO2 per page load
1.7 MB / 2.4 MB budget
1.7 MB transferred
59 requests
0.35 g CO2 per page load
JavaScript 695.6 KiB 41%
Images 485.8 KiB 28%
Fonts 398.5 KiB 23%
CSS 82.1 KiB 5%
HTML 30.2 KiB 2%
Other 11.1 KiB 1%
Other 1.1 KiB 0%
Other 608 B 0%
Other 546 B 0%
0 2.4 MB 4.9 MB
Approaching limit

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

Subset fonts to include only used characters, or switch to system font stacks.

Why this matters

Font payload is large — subset to used glyphs only, or fall back to system fonts (zero load time).

Source: web.dev font loading

B
Image Optimization
18 images, 0 KB saveable
REVIEW
18 images, 0 KB saveable
Info::
All images are well-optimized
18 images 486 KB
0 oversized -0 KB
5 legacy format
0 missing dimensions CLS risk
B
JS Execution Cost
738ms total JS execution
REVIEW
738ms total JS execution
Warning::
https://www.yale.edu/sites/all/themes/yale_blue/js...: 354ms CPU time
Info::
Unattributable: 105ms CPU time
Info::
https://www.googletagmanager.com/gtag/js?id=G-D491...: 96ms CPU time
Info::
https://www.yale.edu/: 71ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-MCL...: 60ms CPU time
Info::
Third-party scripts: 312ms (42% of total)

Main Thread Breakdown

Script Evaluation 45% Other 22% Style & Layout 16% Script Parsing & Compilation 10% Parse HTML & CSS 4%
ScriptTotalScriptingParse/CompileParty
https://www.yale.edu/sites/all/themes/yale_blue/js/site.js?t=202604070135354ms111ms13ms1st
Unattributable105ms2ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-D491W728G4&cx=c&gtm=4e6460h196ms74ms22ms3rd
https://www.yale.edu/71ms21ms5ms1st
https://www.googletagmanager.com/gtm.js?id=GTM-MCLMJ9V60ms45ms14ms3rd
https://www.googletagmanager.com/gtag/js?id=UA-991898-23&l=dataLayer&cx=c51ms37ms14ms3rd
C
JS Bundles
Action
17 scripts, 265 KB unused
REVIEW
17 scripts, 265 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-MCL...: 65 KB unused (52%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=UA-991...: 64 KB unused (56%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.googletagmanager.com/gtag/js?id=G-D491...: 64 KB unused (42%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.yale.edu/sites/all/themes/yale_blue/js...: 38 KB unused (52%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.yale.edu/sites/default/files/googleana...: 34 KB unused (62%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 265 KB
265 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-MCLMJ9V125 KB65 KB (52%)✓3rd
https://www.googletagmanager.com/gtag/js?id=UA-991898-23&l=dataLayer&cx=c115 KB64 KB (56%)✓3rd
https://www.googletagmanager.com/gtag/js?id=G-D491W728G4&cx=c&gtm=4e6460h1153 KB64 KB (42%)✓3rd
https://www.yale.edu/sites/all/themes/yale_blue/js/site.js?t=20260407013573 KB38 KB (52%)✓1st
https://www.yale.edu/sites/default/files/googleanalytics/js?td4wqg55 KB34 KB (62%)✓1st
https://www.yale.edu/sites/default/files/js/js_zDrhTCYsC_8pVOJuGALtlm88oNEaqvyfjVoe0JtAAwI.js19 KB—✗1st
https://www.yale.edu/sites/default/files/js/js_HR7LuITZhSc9MfBClZ7kkiN4YCNnhrdkopJ8rv16Q14.js20 KB—✗1st
https://www.yale.edu/sites/default/files/js/js_f_6-OzlFXjayKlsU5sJKLwjz7LFQvdIZDm-Mt6jKwyM.js1 KB—✓1st
https://www.yale.edu/sites/default/files/js/js_Xp42x4IeuhdbL6uORzJ6WS2Q7LigXFqtOWo49t50sgc.js4 KB—✓1st
https://www.yale.edu/sites/default/files/js/js_rpAwC7cddiEuKQzuro46QwxuNJ50C48xsD6vgW-SmVY.js1 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

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
Third-Party Impact
30% third-party, 0 ms blocking
PASS
30% third-party, 0 ms blocking
Info::
Third-party code accounts for 30% of page weight (513.7 KiB of 1.7 MiB)
Info::
Third-party blocking time is low (0 ms)
70%
30%
First-party Third-party
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
6 fonts (398 KB)
PASS
6 fonts (398 KB)
Info::
6 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

6

398 KB total

Render-blocking

0

of 6

Dominant font-display

swap

Most common across fonts

Font loading timeline
Transfer FOIT (block) FOUT (swap)
0 ms 500 ms 1.0 s FCP 1.0 s LCP 1.3 shttps://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-Medium.woffMallory-Medium.woff https://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-Medium.woff — 74.9 KiB — 0 ms — font-display: swaphttps://www.yale.edu/sites/all/themes/yale_blue/fonts/fontawesome-webfont.woff2?v=4.6.3fontawesome-webfont.woff2 https://www.yale.edu/sites/all/themes/yale_blue/fonts/fontawesome-webfont.woff2?v=4.6.3 — 70.5 KiB — 0 ms — font-display: swaphttps://www.yale.edu/sites/all/themes/yale_blue/fonts/yalenew-roman-webfont.woff2yalenew-roman-webfont.w... https://www.yale.edu/sites/all/themes/yale_blue/fonts/yalenew-roman-webfont.woff2 — 29.4 KiB — 0 ms — font-display: swaphttps://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-Light.woffMallory-Light.woff https://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-Light.woff — 72.6 KiB — 0 ms — font-display: swaphttps://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-LightItalic.woffMallory-LightItalic.woff https://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-LightItalic.woff — 76.3 KiB — 0 ms — font-display: swaphttps://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-Bold.woffMallory-Bold.woff https://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-Bold.woff — 74.8 KiB — 0 ms — font-display: swap
Mallory-Medium.woff woff swap
Size 75 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
fontawesome-webfont.woff2 woff2 swap
Size 71 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
yalenew-roman-webfont.w... woff2 swap
Size 29 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
Mallory-Light.woff woff swap
Size 73 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
Mallory-LightItalic.woff woff swap
Size 76 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
Mallory-Bold.woff woff swap
Size 75 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
  • Convert to woff2 for ~30% smaller file size
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)

Fixing the unchecked items could save ~90 KB and ~180 ms

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=21600 (6 hours)
PASS
max-age=21600 (6 hours)
Info::
Cache-Control header is set
Got: public, max-age=21600
Info::
Effective TTL: 6 hours (max-age=21600)
Info::
ETag present — enables conditional (304) responses
Info::
Last-Modified header present
Cache-Control

public, max-age=21600

DirectiveValueMeaning
public—Any cache may store this response
max-age21600Cache for 6 hours
Effective TTL: 21600 seconds
Network Waterfall
59 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
42% of JavaScript execution is third-party
First-party Third-party 312ms · 393KB · €3/mo
Unattributable
Other
Optional
Execution 105ms
Transfer 0 KB
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 96ms
Transfer 153 KB
Unused 42%
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 60ms
Transfer 125 KB
Unused 52%
Monthly Cost €1/mo
Google Tag Manager
Tag Manager
Optional
Execution 51ms
Transfer 115 KB
Unused 56%
Monthly Cost €1/mo

42% of JavaScript execution time comes from third-party scripts.

Why this matters

Third-party scripts (analytics, ads, social, A/B testing) often dominate execution time — every one is a perf-and-privacy tax.

Learn more ▾

Each third-party script is a black box: you don't control when it loads, what it executes, or how much it grows. They often account for a major share of total blocking time on average sites (HTTP Archive's Web Almanac documents the trend). Audit which ones you actually need, defer the rest, and use facade patterns (lite-youtube, lite-vimeo) for embedded media.

Source: web.dev / HTTP Archive Web Almanac

52% of Google Tag Manager'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

56% of Google Tag Manager'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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