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Performance

· 14 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
84
GRADE
B
FIX
1
REVIEW
3
PASS
8
INFO
2

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

Mobile Desktop
40
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
95
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
77
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.

4.27 s

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

12.14 s

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

910 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.

6.23 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.

12.25 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
8 PASS 3 REVIEW 1 FIX
D
JS Execution Cost
Action
3191ms total JS execution
FIX
3191ms total JS execution
Warning::
https://www.ox.ac.uk/sites/files/oxford/advagg_js/...: 1214ms CPU time
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-TDB...: 504ms CPU time
Warning::
Unattributable: 459ms CPU time
Warning::
https://cc.cdn.civiccomputing.com/9/cookieControl-...: 411ms CPU time
Warning::
https://www.ox.ac.uk/: 403ms CPU time
Info::
Third-party scripts: 1574ms (49% of total)

Main Thread Breakdown

Script Evaluation 42% Style & Layout 25% Other 19% Script Parsing & Compilation 7% Parse HTML & CSS 5%
ScriptTotalScriptingParse/CompileParty
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__ihdwYz7z62m5viS1EMhNOpB9bfVJ_3N7-eC3gKeS-sI__ATnX8WF8ltra-g2RmFaF163qjG6u_xdvxVSENyHJmQk__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js1214ms488ms26ms1st
https://www.googletagmanager.com/gtm.js?id=GTM-TDB29T504ms383ms77ms3rd
Unattributable459ms14ms0ms3rd
https://cc.cdn.civiccomputing.com/9/cookieControl-9.x.min.js411ms344ms66ms3rd
https://www.ox.ac.uk/403ms16ms5ms1st
https://sjs.bizographics.com/insight.min.js134ms107ms8ms3rd
https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da177152312451666ms41ms5ms3rd
B
Page Weight Budget
1.5 MB transferred, 60 requests
REVIEW
1.5 MB transferred, 60 requests
Info::
Page weighs 2.9 MB (1.5 MB transferred)
Info::
60 HTTP requests
Info::
Estimated 0.32 g CO2 per page load
1.5 MB / 2.4 MB budget
1.5 MB transferred
60 requests
0.32 g CO2 per page load
Images 925.8 KiB 59%
JavaScript 404.0 KiB 26%
Fonts 141.4 KiB 9%
CSS 63.9 KiB 4%
HTML 19.4 KiB 1%
Other 2.3 KiB 0%
Other 2.2 KiB 0%
0 2.4 MB 4.9 MB
Approaching limit
B
Image Optimization
31 images, 0 KB saveable
REVIEW
31 images, 0 KB saveable
Info::
All images are well-optimized
31 images 926 KB
0 oversized -0 KB
6 legacy format
0 missing dimensions CLS risk
C
JS Bundles
Action
11 scripts, 147 KB unused
REVIEW
11 scripts, 147 KB unused
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-TDB...: 66 KB unused (48%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://cc.cdn.civiccomputing.com/9/cookieControl-...: 57 KB unused (46%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.ox.ac.uk/sites/files/oxford/advagg_js/...: 24 KB unused (51%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.ox.ac.uk/sites/files/oxford/advagg_js/...: unminified — 13 KB could be saved
Warning::
https://www.ox.ac.uk/sites/files/oxford/advagg_js/...: unminified — 10 KB could be saved
Info::
Total unused JavaScript: 147 KB
147 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.googletagmanager.com/gtm.js?id=GTM-TDB29T138 KB66 KB (48%)✓3rd
https://cc.cdn.civiccomputing.com/9/cookieControl-9.x.min.js123 KB57 KB (46%)✓3rd
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__9q_RhUzRB9SYU1-amhF7x_iVsHaJWYLCy9mGerNNw8c__r14_gMXz1ZbCtJf3hugZI-ClIj-6kYYT4Zc-iywNTA4__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js46 KB24 KB (51%)✗1st
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__SlxZR0T0y0knhPGspoKKlEQqbk_RdNNsHwLrlCQRTSo__jRyIJdNHHPQDI24D74GCcZq-Uqnrf4Vs1Wh5VKn50M0__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js1 KB—✓1st
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__ihdwYz7z62m5viS1EMhNOpB9bfVJ_3N7-eC3gKeS-sI__ATnX8WF8ltra-g2RmFaF163qjG6u_xdvxVSENyHJmQk__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js45 KB—✗1st
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__z5ONFBC5kmHZRZuHWswENYjC0rzf40bh_hB_Fs0eyLo__WcT3Q2crdrKi2EHa4S2isbSrXXO5RbKkDpvVkjhTmaY__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js10 KB—✗1st
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__9o6MTP80DXWHri8ze4nKy9qC5QYGmn5CmTwGsjeqoRs__t7QMh2Q0VAdZOqg2nX8lHHSSz0oEF4l8S4NpWKqSdpE__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js1 KB—✓1st
https://www.ox.ac.uk/sites/files/oxford/advagg_js/js__g6HAL4XtohiHzS9CG4SIugqNOzdAq58xVph4DbYxlNE__o1_7j2Bpaj2feiS_rkUK_CGonKU4T-Mdv49O47LYHOc__h7T-cjtV_dUO9EYp5xzvQZuTpmuCIt2rzPKmYSUARw8.js13 KB—✗1st
https://static.cloudflareinsights.com/beacon.min.js/v8c78df7c7c0f484497ecbca7046644da177152312451611 KB—✓3rd
https://sjs.bizographics.com/insight.min.js17 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

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+
Third-Party Impact
19% third-party, 0 ms blocking
PASS
19% third-party, 0 ms blocking
Info::
Third-party code accounts for 19% of page weight (292.2 KiB of 1.5 MiB)
Info::
Third-party blocking time is low (0 ms)
81%
19%
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
3 fonts (141 KB)
PASS
3 fonts (141 KB)
Info::
3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

3

141 KB total

Render-blocking

0

of 3

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 4.3 s LCP 12.1 shttps://www.ox.ac.uk/cf-fonts/s/pt-sans/5.0.11/latin/400/normal.woff2normal.woff2 https://www.ox.ac.uk/cf-fonts/s/pt-sans/5.0.11/latin/400/normal.woff2 — 44.7 KiB — 0 ms — font-display: swaphttps://www.ox.ac.uk/cf-fonts/s/pt-sans/5.0.11/latin/700/normal.woff2normal.woff2 https://www.ox.ac.uk/cf-fonts/s/pt-sans/5.0.11/latin/700/normal.woff2 — 46.3 KiB — 0 ms — font-display: swaphttps://www.ox.ac.uk/cf-fonts/s/pt-sans-narrow/5.0.19/latin/700/normal.woff2normal.woff2 https://www.ox.ac.uk/cf-fonts/s/pt-sans-narrow/5.0.19/latin/700/normal.woff2 — 50.4 KiB — 0 ms — font-display: swap
normal.woff2 woff2 swap
Size 45 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
normal.woff2 woff2 swap
Size 46 KB
Load time 0 ms
Start 0 ms
Risk FOUT — text flashes from fallback to web font
normal.woff2 woff2 swap
Size 50 KB
Load time 0 ms
Start 0 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+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

A+
HTTP Caching
max-age=1800 (30 minutes)
PASS
max-age=1800 (30 minutes)
Info::
Cache-Control header is set
Got: public, max-age=1800
Info::
Effective TTL: 30 minutes (max-age=1800)
Info::
Last-Modified header present
Cache-Control

public, max-age=1800

DirectiveValueMeaning
public—Any cache may store this response
max-age1800Cache for 30 minutes
Effective TTL: 1800 seconds
Network Waterfall
60 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
49% of JavaScript execution is third-party
First-party Third-party 1574ms · 289KB · £16/mo
Google Tag Manager
Tag Manager
Costly
Execution 504ms
Transfer 138 KB
Unused 48%
Monthly Cost £5/mo
Unattributable
Other
Costly
Execution 459ms
Transfer 0 KB
Monthly Cost £5/mo
cc.cdn.civiccomputing.com
Other
Costly
Execution 411ms
Transfer 123 KB
Unused 46%
Monthly Cost £4/mo
sjs.bizographics.com
Other
Optional
Execution 134ms
Transfer 17 KB
Monthly Cost £1/mo
static.cloudflareinsights.com
Other
Optional
Execution 66ms
Transfer 11 KB
Monthly Cost £1/mo

These scripts may cost more than they're worth

  • Google Tag Manager adds 504ms and costs ~£5/month
  • Unattributable adds 459ms and costs ~£5/month
  • cc.cdn.civiccomputing.com adds 411ms and costs ~£4/month

49% 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

Google Tag Manager takes 504ms 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 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

cc.cdn.civiccomputing.com takes 411ms 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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