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https://cambridge.org

Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
89
GRADE
B
FIX
2
REVIEW
0
PASS
11
INFO
2

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

Mobile Desktop
98
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
91
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
92
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
50
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.

482 ms

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

985 ms

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

69 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.

482 ms

Time to Interactive Time to Interactive — how long until the page is fully interactive and responds to user input. Under 3.8s is good.

985 ms

Page Load Progression

421 ms
842 ms
1.3 s
1.7 s
2.1 s
2.5 s
2.9 s
3.4 s
Checks
15
11 PASS 2 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 (499.2 KiB of 499.5 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
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.

A+
Page Weight Budget
500 KB transferred, 22 requests
PASS
500 KB transferred, 22 requests
Info::
Page weighs 896 KB (500 KB transferred)
Info::
22 HTTP requests
Info::
Estimated 0.10 g CO2 per page load
500 KB / 2.4 MB budget
500 KB transferred
22 requests
0.10 g CO2 per page load
Other 308.1 KiB 62%
HTML 99.8 KiB 20%
JavaScript 87.5 KiB 18%
Images 2.0 KiB 0%
Other 1.7 KiB 0%
Other 389 B 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
Image Optimization
3 images, 0 KB saveable
PASS
3 images, 0 KB saveable
Info::
All images are well-optimized
3 images 2 KB
0 oversized -0 KB
3 legacy format
0 missing dimensions CLS risk
A+
JS Execution Cost
491ms total JS execution
PASS
491ms total JS execution
Warning::
https://www.cambridge.org/cdn-cgi/challenge-platfo...: 439ms CPU time
Info::
Unattributable: 53ms CPU time
Warning::
Third-party scripts: 491ms (100% of total)

Main Thread Breakdown

Script Evaluation 81% Other 11%
ScriptTotalScriptingParse/CompileParty
https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed51375e8bafd91439ms419ms6ms3rd
Unattributable53ms2ms0ms3rd
A+
Font Loading
No web fonts (system fonts)
PASS
No web fonts (system fonts)
Info::
No web fonts loaded — system fonts are fastest
No web fonts loaded — system fonts are optimal.
A+
JS Bundles
10 scripts, 0 KB unused
PASS
10 scripts, 0 KB unused
0 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed51375e8bafd9170 KB—✓3rd
blob:https://www.cambridge.org/e53fa1c2-7282-4f83-af85-8721ffa937df0 KB—✓3rd
https://challenges.cloudflare.com/turnstile/v0/g/b0a7532ac8ec/api.js?onload=cFyL2&render=explicit17 KB—✓3rd
blob:https://www.cambridge.org/88269522-88b6-455c-aa0a-f47e1709ab38-0 KB—✓3rd
blob:https://challenges.cloudflare.com/5490cd4e-1c97-43ae-94f2-83fbda1929e70 KB—✓3rd
blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910-0 KB—✓3rd
blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910-0 KB—✓3rd
blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910-0 KB—✓3rd
blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b079100 KB—✓3rd
blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b079100 KB—✓3rd
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
22 resources · 500 KB · 0 KB savings available
PASS
22 resources · 500 KB · 0 KB savings available
Info::
Within 1MB page-weight target
Got: 500 KB
Warning::
20 third-party resources (100% of weight)
Info::
1 resources over 200KB
22 resources · 499.5 KiB · 20 third-party Within 1MB page-weight target
Other 62% · 310.2 KiB
Document 20% · 99.8 KiB
JavaScript 18% · 87.5 KiB
Image 0% · 2.0 KiB
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

Network Waterfall
22 requests over 2497ms
INFO
0 ms 500 ms 1.0 s 1.5 s 2.0 s 2.5 s FCP 482 ms LCP 985 mshttps://cambridge.org// https://cambridge.org/ — 301 — 326 B — 20 ms — h2https://www.cambridge.org/www.cambridge.org/ https://www.cambridge.org/ — 307 — 63 B — 20 ms — http/1.1https://cambridge.org// https://cambridge.org/ — 301 — 0 B — 1 ms — h2https://www.cambridge.org/www.cambridge.org/ https://www.cambridge.org/ — 403 — 3.5 KiB — 6 ms — h2https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed51375e8bafd91www.cambridge.org/cdn-cgi/challenge... https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed51375e8bafd91 — 200 — 70.1 KiB — 19 ms — h2blob:https://www.cambridge.org/e53fa1c2-7282-4f83-af85-8721ffa937dfwww.cambridge.org/e53fa1c2-7282-4f8... blob:https://www.cambridge.org/e53fa1c2-7282-4f83-af85-8721ffa937df — -1 — 0 B — 0 ms — https://challenges.cloudflare.com/turnstile/v0/g/b0a7532ac8ec/api.js?onload=cFyL2&render=explicitchallenges.cloudflare.com/turnstile... https://challenges.cloudflare.com/turnstile/v0/g/b0a7532ac8ec/api.js?onload=cFyL2&render=explicit — 200 — 17.4 KiB — 23 ms — h3https://www.cambridge.org/favicon.icowww.cambridge.org/favicon.ico https://www.cambridge.org/favicon.ico — 200 — 1.3 KiB — 18 ms — h2https://www.cambridge.org/favicon.icowww.cambridge.org/favicon.ico https://www.cambridge.org/favicon.ico — 200 — 0 B — 2 ms — h2https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/flow/ov1/2582455831:1776359653:dhx-9h23FmH10TlLu5PxT4ZpfX2Ps-EPhrGZOBMjK-4/9ed51375e8bafd91/T32ZC9RqQ__1_cFEWuaa3qtMSUxjznel_jianRu4Gf8-1776362284-1.2.1.1-WSrHnKwWqyDUC3NlLYT4uzRtArfcWvp3_Cukzys6__IsiA8HGZau.CDS1Sb3Brw1www.cambridge.org/cdn-cgi/challenge... https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/flow/ov1/2582455831:1776359653:dhx-9h23FmH10TlLu5PxT4ZpfX2Ps-EPhrGZOBMjK-4/9ed51375e8bafd91/T32ZC9RqQ__1_cFEWuaa3qtMSUxjznel_jianRu4Gf8-1776362284-1.2.1.1-WSrHnKwWqyDUC3NlLYT4uzRtArfcWvp3_Cukzys6__IsiA8HGZau.CDS1Sb3Brw1 — 200 — 13.7 KiB — 16 ms — h2blob:https://www.cambridge.org/88269522-88b6-455c-aa0a-f47e1709ab38www.cambridge.org/88269522-88b6-455... blob:https://www.cambridge.org/88269522-88b6-455c-aa0a-f47e1709ab38 — 200 — -1 B — 46 ms — blobhttps://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/turnstile/f/ov2/av0/rch/cotj3/0x4AAAAAAADnPIDROrmt1Wwj/light/fbE/new/normal?lang=autochallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/turnstile/f/ov2/av0/rch/cotj3/0x4AAAAAAADnPIDROrmt1Wwj/light/fbE/new/normal?lang=auto — 200 — 96.4 KiB — 34 ms — h3https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/cmg/1challenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/cmg/1 — 200 — 208 B — 7 ms — h3blob:https://challenges.cloudflare.com/5490cd4e-1c97-43ae-94f2-83fbda1929e7challenges.cloudflare.com/5490cd4e-... blob:https://challenges.cloudflare.com/5490cd4e-1c97-43ae-94f2-83fbda1929e7 — -1 — 0 B — 0 ms — https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/flow/ov1/2665393735:1776359655:-yZ21BwzAphqzXrHgKcxOX77RkXAL9rAafXdddf9JJc/9ed5137839ba3dee/o08zB.HJ.hQE7EJ.v8jIwwryeg23ztcvBENfPoQ2CP8-1776362284-1.2.1.1-ky30k.cbR8dGvNzFNBIQUQ1awgZvY_IzJon0RRkIiMFZNBV5qZgAn9_A5HyLES5Pchallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/flow/ov1/2665393735:1776359655:-yZ21BwzAphqzXrHgKcxOX77RkXAL9rAafXdddf9JJc/9ed5137839ba3dee/o08zB.HJ.hQE7EJ.v8jIwwryeg23ztcvBENfPoQ2CP8-1776362284-1.2.1.1-ky30k.cbR8dGvNzFNBIQUQ1awgZvY_IzJon0RRkIiMFZNBV5qZgAn9_A5HyLES5P — 200 — 294.4 KiB — 145 ms — h3blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910challenges.cloudflare.com/6a88ffd7-... blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910 — 200 — -1 B — 120 ms — blobblob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910challenges.cloudflare.com/6a88ffd7-... blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910 — 200 — -1 B — 26 ms — blobhttps://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/d/9ed5137839ba3dee/1776362285177/idBzpDM87b-ctCxchallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/d/9ed5137839ba3dee/1776362285177/idBzpDM87b-ctCx — 200 — 563 B — 10 ms — h3blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910challenges.cloudflare.com/6a88ffd7-... blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910 — 200 — -1 B — 29 ms — blobblob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910challenges.cloudflare.com/6a88ffd7-... blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910 — -1 — 0 B — 0 ms — blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910challenges.cloudflare.com/6a88ffd7-... blob:https://challenges.cloudflare.com/6a88ffd7-94c6-4aed-927e-519fc0b07910 — -1 — 0 B — 0 ms — https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/pat/9ed5137839ba3dee/1776362285177/b71c864f07014f9300bf7e5abba31930d0d6eea0a1ef781a243b684219b7ce71/spo6evbYw2tK5lechallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/pat/9ed5137839ba3dee/1776362285177/b71c864f07014f9300bf7e5abba31930d0d6eea0a1ef781a243b684219b7ce71/spo6evbYw2tK5le — 401 — 1.7 KiB — 6 ms — h3
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 491ms · 70KB · $7/mo
www.cambridge.org
Other
Costly
Execution 439ms
Transfer 70 KB
Monthly Cost $6/mo
Unattributable
Other
Optional
Execution 53ms
Transfer 0 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • www.cambridge.org adds 439ms and costs ~$6/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.cambridge.org takes 439ms 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

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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