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Performance

· 16 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
86
GRADE
B
FIX
1
REVIEW
4
PASS
9
INFO
2

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

Mobile Desktop
38
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
88
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.

5.20 s

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

12.73 s

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

988 ms

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

0.000

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

6.37 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.

12.77 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
16
9 PASS 4 REVIEW 1 FIX
D
JS Execution Cost
Action
3449ms total JS execution
FIX
3449ms total JS execution
Warning::
https://www.yale.edu/sites/all/themes/yale_blue/js...: 877ms CPU time
Warning::
https://ajax.googleapis.com/ajax/libs/jquery/1.10....: 459ms CPU time
Warning::
Unattributable: 422ms CPU time
Warning::
https://www.googletagmanager.com/gtag/js?id=G-D491...: 387ms CPU time
Info::
https://www.googletagmanager.com/gtm.js?id=GTM-MCL...: 218ms CPU time
Warning::
Third-party scripts: 2147ms (62% of total)

Main Thread Breakdown

Script Evaluation 47% Other 23% Style & Layout 14% Script Parsing & Compilation 11% Parse HTML & CSS 5%
ScriptTotalScriptingParse/CompileParty
https://www.yale.edu/sites/all/themes/yale_blue/js/site.js?t=202604070135877ms396ms50ms1st
https://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js459ms106ms20ms3rd
Unattributable422ms12ms0ms3rd
https://www.googletagmanager.com/gtag/js?id=G-D491W728G4&cx=c&gtm=4e6460387ms311ms73ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MCLMJ9V218ms165ms51ms3rd
https://www.googletagmanager.com/gtag/js?id=UA-991898-23&l=dataLayer&cx=c208ms138ms68ms3rd
https://www.yale.edu/205ms91ms22ms1st
https://js-agent.newrelic.com/nr-rum-1.312.1.min.js185ms157ms9ms3rd
https://siteimproveanalytics.com/js/siteanalyze_66356571.js184ms93ms29ms3rd
https://www.yale.edu/sites/default/files/googleanalytics/js?td4wqg110ms52ms26ms1st

Showing top 10 of 13 scripts

B
Page Weight Budget
1.4 MB transferred, 58 requests
REVIEW
1.4 MB transferred, 58 requests
Info::
Page weighs 3.0 MB (1.4 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 399 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 399 KB
Info::
58 HTTP requests
Info::
Estimated 0.30 g CO2 per page load
1.4 MB / 2.4 MB budget
1.4 MB transferred
58 requests
0.30 g CO2 per page load
JavaScript 695.5 KiB 48%
Fonts 398.5 KiB 27%
Images 242.5 KiB 17%
CSS 82.2 KiB 6%
HTML 30.2 KiB 2%
Other 11.0 KiB 1%
Other 1.1 KiB 0%
Other 610 B 0%
Other 546 B 0%
0 2.4 MB 4.9 MB
Under budget

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
17 images, 0 KB saveable
REVIEW
17 images, 0 KB saveable
Info::
All images are well-optimized
17 images 242 KB
0 oversized -0 KB
4 legacy format
0 missing dimensions CLS risk
C
JS Bundles
Action
17 scripts, 264 KB unused
REVIEW
17 scripts, 264 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: 264 KB
264 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=4e6460153 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
35% third-party, 0 ms blocking
PASS
35% third-party, 0 ms blocking
Info::
Third-party code accounts for 35% of page weight (513.7 KiB of 1.4 MiB)
Info::
Third-party blocking time is low (0 ms)
65%
35%
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 (399 KB)
PASS
6 fonts (399 KB)
Info::
6 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

6

399 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 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s FCP 5.2 s LCP 12.7 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 — 74.8 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-LightItalic.woffMallory-LightItalic.woff https://www.yale.edu/sites/all/themes/yale_blue/fonts_new/Mallory/Mallory/Mallory-LightItalic.woff — 76.4 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-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-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-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-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+
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+
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
58 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
62% of JavaScript execution is third-party
First-party Third-party 2147ms · 504KB · €23/mo
ajax.googleapis.com
Other
Costly
Execution 459ms
Transfer 33 KB
Monthly Cost €5/mo
Unattributable
Other
Costly
Execution 422ms
Transfer 0 KB
Monthly Cost €5/mo
Google Tag Manager
Tag Manager
Costly
Execution 387ms
Transfer 153 KB
Unused 42%
Monthly Cost €4/mo
Google Tag Manager
Tag Manager
Costly
Execution 218ms
Transfer 125 KB
Unused 52%
Monthly Cost €2/mo
Google Tag Manager
Tag Manager
Costly
Execution 208ms
Transfer 115 KB
Unused 56%
Monthly Cost €2/mo
js-agent.newrelic.com
Other
Optional
Execution 185ms
Transfer 18 KB
Monthly Cost €2/mo
siteimproveanalytics.com
Other
Optional
Execution 184ms
Transfer 39 KB
Monthly Cost €2/mo
Google Analytics
Analytics
Optional
Execution 83ms
Transfer 21 KB
Monthly Cost €1/mo

These scripts may cost more than they're worth

  • ajax.googleapis.com adds 459ms and costs ~€5/month
  • Unattributable adds 422ms and costs ~€5/month
  • Google Tag Manager adds 387ms and costs ~€4/month
  • Google Tag Manager adds 218ms and costs ~€2/month
  • Google Tag Manager adds 208ms and costs ~€2/month

62% 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

ajax.googleapis.com takes 459ms 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 422ms 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 387ms 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 218ms 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

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

Google Tag Manager takes 208ms 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

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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