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https://cambridge.org

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
89
GRADE
B
FIX
3
REVIEW
0
PASS
12
INFO
2

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

Mobile Desktop
64
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.

1.71 s

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

3.58 s

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

1.45 s

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

0.002

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

1.71 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.

4.48 s

Page Load Progression

441 ms
882 ms
1.3 s
1.8 s
2.2 s
2.6 s
3.1 s
3.5 s
Checks
17
12 PASS 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 (507.6 KiB of 507.9 KiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
JS Execution Cost
Action
2259ms total JS execution
FIX
2259ms total JS execution
Warning::
https://www.cambridge.org/cdn-cgi/challenge-platfo...: 1905ms CPU time
Info::
Unattributable: 247ms CPU time
Info::
https://www.cambridge.org/: 107ms CPU time
Warning::
Third-party scripts: 2259ms (100% of total)

Main Thread Breakdown

Script Evaluation 82% Other 12%
ScriptTotalScriptingParse/CompileParty
https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed513166fa2243f1905ms1838ms25ms3rd
Unattributable247ms9ms0ms3rd
https://www.cambridge.org/107ms13ms2ms3rd
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
508 KB transferred, 24 requests
PASS
508 KB transferred, 24 requests
Info::
Page weighs 902 KB (508 KB transferred)
Info::
24 HTTP requests
Info::
Estimated 0.10 g CO2 per page load
508 KB / 2.4 MB budget
508 KB transferred
24 requests
0.10 g CO2 per page load
Other 317.0 KiB 62%
HTML 97.0 KiB 19%
JavaScript 87.7 KiB 17%
Images 4.2 KiB 1%
Other 1.7 KiB 0%
Other 391 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 4 KB
0 oversized -0 KB
3 legacy format
0 missing dimensions CLS risk
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
11 scripts, 0 KB unused
PASS
11 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=9ed513166fa2243f70 KB—✓3rd
blob:https://www.cambridge.org/41ffb330-444e-4968-abf5-d0534f512e660 KB—✓3rd
https://challenges.cloudflare.com/turnstile/v0/g/b0a7532ac8ec/api.js?onload=cFyL2&render=explicit17 KB—✓3rd
blob:https://www.cambridge.org/31c03b3f-2e31-4bdb-a558-06474796a970-0 KB—✓3rd
blob:https://challenges.cloudflare.com/3a946887-d963-44d8-bf2e-723163a709bd0 KB—✓3rd
blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d-0 KB—✓3rd
blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d-0 KB—✓3rd
blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d-0 KB—✓3rd
blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d-0 KB—✓3rd
blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d-0 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
24 resources · 508 KB · 0 KB savings available
PASS
24 resources · 508 KB · 0 KB savings available
Info::
Within 1MB page-weight target
Got: 508 KB
Warning::
22 third-party resources (100% of weight)
Info::
1 resources over 200KB
24 resources · 507.9 KiB · 22 third-party Within 1MB page-weight target
Other 63% · 319.0 KiB
Document 19% · 97.0 KiB
JavaScript 17% · 87.7 KiB
Image 1% · 4.2 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: Cloudflare

Network Waterfall
24 requests over 3102ms
INFO
0 ms 1.0 s 2.0 s 3.0 s FCP 1.7 s LCP 3.6 shttps://cambridge.org// https://cambridge.org/ — 301 — 328 B — 16 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 — 7 ms — h2https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed513166fa2243fwww.cambridge.org/cdn-cgi/challenge... https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9ed513166fa2243f — 200 — 70.3 KiB — 22 ms — h2blob:https://www.cambridge.org/41ffb330-444e-4968-abf5-d0534f512e66www.cambridge.org/41ffb330-444e-496... blob:https://www.cambridge.org/41ffb330-444e-4968-abf5-d0534f512e66 — -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 — 22 ms — h3https://www.cambridge.org/favicon.icowww.cambridge.org/favicon.ico https://www.cambridge.org/favicon.ico — 200 — 1.3 KiB — 17 ms — h2https://www.cambridge.org/favicon.icowww.cambridge.org/favicon.ico https://www.cambridge.org/favicon.ico — 200 — 0 B — 1 ms — h2https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/flow/ov1/2582455831:1776359653:dhx-9h23FmH10TlLu5PxT4ZpfX2Ps-EPhrGZOBMjK-4/9ed513166fa2243f/jc6gKnm0WJ6MHyZQb6by3b1HrlKHpg.vOkxQ7c3A_9c-1776362269-1.2.1.1-hRPJIFkApvLKRTA_GLQOUKzWf_mEwPWm8j1SMOR3PvbhuxFP4486b3jZUoJSPjCAwww.cambridge.org/cdn-cgi/challenge... https://www.cambridge.org/cdn-cgi/challenge-platform/h/g/flow/ov1/2582455831:1776359653:dhx-9h23FmH10TlLu5PxT4ZpfX2Ps-EPhrGZOBMjK-4/9ed513166fa2243f/jc6gKnm0WJ6MHyZQb6by3b1HrlKHpg.vOkxQ7c3A_9c-1776362269-1.2.1.1-hRPJIFkApvLKRTA_GLQOUKzWf_mEwPWm8j1SMOR3PvbhuxFP4486b3jZUoJSPjCA — 200 — 13.7 KiB — 19 ms — h2blob:https://www.cambridge.org/31c03b3f-2e31-4bdb-a558-06474796a970www.cambridge.org/31c03b3f-2e31-4bd... blob:https://www.cambridge.org/31c03b3f-2e31-4bdb-a558-06474796a970 — 200 — -1 B — 43 ms — blobhttps://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/turnstile/f/ov2/av0/rch/exqts/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/exqts/0x4AAAAAAADnPIDROrmt1Wwj/light/fbE/new/normal?lang=auto — 200 — 93.5 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 — 209 B — 6 ms — h3blob:https://challenges.cloudflare.com/3a946887-d963-44d8-bf2e-723163a709bdchallenges.cloudflare.com/3a946887-... blob:https://challenges.cloudflare.com/3a946887-d963-44d8-bf2e-723163a709bd — -1 — 0 B — 0 ms — https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/flow/ov1/2665393735:1776359655:-yZ21BwzAphqzXrHgKcxOX77RkXAL9rAafXdddf9JJc/9ed51318ea18fd40/FUJLziURjuJJesbjMmm5Fqli2JQAuZFV0SSmyYIRVfg-1776362269-1.2.1.1-WVX5rCY.ynyxb_I6GwBtrdeEuCi4gziFAz6YYmqM.brUk36lyhAxHZp8SUCQjkBfchallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/flow/ov1/2665393735:1776359655:-yZ21BwzAphqzXrHgKcxOX77RkXAL9rAafXdddf9JJc/9ed51318ea18fd40/FUJLziURjuJJesbjMmm5Fqli2JQAuZFV0SSmyYIRVfg-1776362269-1.2.1.1-WVX5rCY.ynyxb_I6GwBtrdeEuCi4gziFAz6YYmqM.brUk36lyhAxHZp8SUCQjkBf — 200 — 280.4 KiB — 115 ms — h3blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872dchallenges.cloudflare.com/48b45b5b-... blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d — 200 — -1 B — 100 ms — blobblob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872dchallenges.cloudflare.com/48b45b5b-... blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d — 200 — -1 B — 47 ms — blobblob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872dchallenges.cloudflare.com/48b45b5b-... blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d — 200 — -1 B — 26 ms — blobblob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872dchallenges.cloudflare.com/48b45b5b-... blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d — 200 — -1 B — 21 ms — blobblob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872dchallenges.cloudflare.com/48b45b5b-... blob:https://challenges.cloudflare.com/48b45b5b-4d77-44c2-902a-ea3b2150872d — 200 — -1 B — 23 ms — blobhttps://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/pat/9ed51318ea18fd40/1776362269915/e054d18eee875535eff2006baae981e4b70c054e9e91c633937194aef585d2a7/RAZFOnMUR-4rL4qchallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/pat/9ed51318ea18fd40/1776362269915/e054d18eee875535eff2006baae981e4b70c054e9e91c633937194aef585d2a7/RAZFOnMUR-4rL4q — 401 — 1.7 KiB — 7 ms — h3https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/d/9ed51318ea18fd40/1776362269915/Gz7DnwuXgb5SEXKchallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/d/9ed51318ea18fd40/1776362269915/Gz7DnwuXgb5SEXK — 200 — 2.7 KiB — 7 ms — h3https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/flow/ov1/2665393735:1776359655:-yZ21BwzAphqzXrHgKcxOX77RkXAL9rAafXdddf9JJc/9ed51318ea18fd40/FUJLziURjuJJesbjMmm5Fqli2JQAuZFV0SSmyYIRVfg-1776362269-1.2.1.1-WVX5rCY.ynyxb_I6GwBtrdeEuCi4gziFAz6YYmqM.brUk36lyhAxHZp8SUCQjkBfchallenges.cloudflare.com/cdn-cgi/c... https://challenges.cloudflare.com/cdn-cgi/challenge-platform/h/g/flow/ov1/2665393735:1776359655:-yZ21BwzAphqzXrHgKcxOX77RkXAL9rAafXdddf9JJc/9ed51318ea18fd40/FUJLziURjuJJesbjMmm5Fqli2JQAuZFV0SSmyYIRVfg-1776362269-1.2.1.1-WVX5rCY.ynyxb_I6GwBtrdeEuCi4gziFAz6YYmqM.brUk36lyhAxHZp8SUCQjkBf — 200 — 22.8 KiB — 28 ms — h3blob:https://challenges.cloudflare.com/865e67ac-0349-42d0-be94-436f2f6aa6cachallenges.cloudflare.com/865e67ac-... blob:https://challenges.cloudflare.com/865e67ac-0349-42d0-be94-436f2f6aa6ca — 200 — -1 B — 23 ms — blob
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 2259ms · 74KB · $30/mo
www.cambridge.org
Other
Costly
Execution 1905ms
Transfer 70 KB
Monthly Cost $25/mo
Unattributable
Other
Costly
Execution 247ms
Transfer 0 KB
Monthly Cost $3/mo
www.cambridge.org
Other
Optional
Execution 107ms
Transfer 3 KB
Monthly Cost $1/mo

These scripts may cost more than they're worth

  • www.cambridge.org adds 1905ms and costs ~$25/month
  • Unattributable adds 247ms and costs ~$3/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 1905ms 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 247ms 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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