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https://bris.ac.uk

Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
70
GRADE
C
FIX
6
REVIEW
1
PASS
8
INFO
2

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

Mobile Desktop
29
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
96
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.

7.42 s

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

24.75 s

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

1.78 s

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

0.023

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

9.98 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.

24.75 s

Page Load Progression

502 ms
1.0 s
1.5 s
2.0 s
2.5 s
3.0 s
3.5 s
4.0 s
Checks
17
8 PASS 1 REVIEW 6 FIX
F
Page Weight Budget
Action
4.0 MB transferred, 60 requests
FIX
4.0 MB transferred, 60 requests
Critical::
Page weighs 5.9 MB (4.0 MB transferred)
Info::
Fonts are 1.8 MB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 1.8 MB
Warning::
JavaScript is 1.2 MB — consider code splitting or lazy loading
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
Got: 1.2 MB
Info::
60 HTTP requests
Info::
Estimated 0.84 g CO2 per page load
4.0 MB / 2.4 MB budget
4.0 MB transferred
60 requests
0.84 g CO2 per page load
Fonts 1.8 MiB 45%
JavaScript 1.2 MiB 31%
Images 528.4 KiB 13%
CSS 197.5 KiB 5%
Other 175.5 KiB 4%
HTML 87.7 KiB 2%
Other 11.5 KiB 0%
Other 1004 B 0%
Other 44 B 0%
Other 21 B 0%
Other 0 B 0%
0 2.4 MB 4.9 MB
Over budget

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

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

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 (4.0 MiB of 4.0 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
F
JS Execution Cost
Action
5256ms total JS execution
FIX
5256ms total JS execution
Warning::
https://www.bristol.ac.uk/: 1753ms CPU time
Warning::
Unattributable: 1205ms CPU time
Warning::
https://www.googletagmanager.com/gtm.js?id=GTM-MWC...: 633ms CPU time
Warning::
https://eu.gw.fortiabp.forticloud.com/api/v1/gw/st...: 612ms CPU time
Warning::
https://app.termly.io/resource-blocker/f00d1986-fa...: 486ms CPU time
Warning::
Third-party scripts: 5256ms (100% of total)

Main Thread Breakdown

Script Evaluation 44% Other 21% Style & Layout 21% Rendering 7% Script Parsing & Compilation 5%
ScriptTotalScriptingParse/CompileParty
https://www.bristol.ac.uk/1753ms19ms3ms3rd
Unattributable1205ms555ms0ms3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MWCJ929633ms508ms92ms3rd
https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/vendor.www_bristol_ac_uk.hHsrG.v1768494982.js612ms403ms1ms3rd
https://app.termly.io/resource-blocker/f00d1986-fa46-46cf-a165-30f04408b1ce?autoBlock=on486ms389ms59ms3rd
https://app.termly.io/resource-blocker/f00d1986-fa46-46cf-a165-30f04408b1ce163ms103ms59ms3rd
https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-main-2.7.0.js128ms48ms2ms3rd
https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/app.12148122.js109ms107ms2ms3rd
https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-vendors.a3cb5fa7.js83ms45ms29ms3rd
https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-480a6038.24fe62bd.js82ms60ms22ms3rd
F
JS Bundles
Action
35 scripts, 714 KB unused
FIX
35 scripts, 714 KB unused
Warning::
https://eu.gw.fortiabp.forticloud.com/api/v1/gw/st...: 142 KB unused (48%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.bristol.ac.uk/assets/homepage-search/1...: 94 KB unused (69%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.bristol.ac.uk/assets/homepage-search/1...: 94 KB unused (69%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://app.termly.io/resource-blocker/f00d1986-fa...: 82 KB unused (58%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.bristol.ac.uk/assets/responsive-web-pr...: 71 KB unused (94%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 714 KB
714 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/main.www_bristol_ac_uk.hHsrG.v1768494982.js295 KB142 KB (48%)✓3rd
https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-480a6038.24fe62bd.js137 KB94 KB (69%)✓3rd
https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-480a6038.24fe62bd.js0 KB94 KB (69%)✓3rd
https://app.termly.io/resource-blocker/f00d1986-fa46-46cf-a165-30f04408b1ce143 KB82 KB (58%)✓3rd
https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-slider-2.7.0.js76 KB71 KB (94%)✓3rd
https://www.googletagmanager.com/gtm.js?id=GTM-MWCJ929195 KB57 KB (30%)✓3rd
https://app.termly.io/resource-blocker/f00d1986-fa46-46cf-a165-30f04408b1ce?autoBlock=on144 KB53 KB (37%)✓3rd
https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-vendors.a3cb5fa7.js124 KB46 KB (38%)✓3rd
https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/vendor.www_bristol_ac_uk.hHsrG.v1768494982.js75 KB43 KB (57%)✓3rd
https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-vimeo-2.7.0.js39 KB30 KB (78%)✓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

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

F
Page Weight Inventory
Action
60 resources · 4.0 MB · 714 KB savings available
FIX
60 resources · 4.0 MB · 714 KB savings available
Warning::
Page weight 3.0 MB over 1MB target
Got: 4.0 MB Expected: ≤ 1 MB
Info::
~714 KB of savings available
Warning::
59 third-party resources (100% of weight)
Info::
4 resources over 200KB
60 resources · 4.0 MiB · 59 third-party 3.0 MiB over 1MB target
Font 45% · 1.8 MiB
JavaScript 35% · 1.4 MiB
Image 13% · 543.5 KiB
CSS 5% · 197.5 KiB
Document 2% · 87.7 KiB
Other 0% · 12.7 KiB

~713.7 KiB of savings available

Remove unused JavaScript: 713.7 KiB
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.

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

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 528 KB
0 oversized -0 KB
2 legacy format
0 missing dimensions CLS risk
A+
Font Loading
4 fonts (1853 KB)
PASS
4 fonts (1853 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

1853 KB total

Render-blocking

0

of 4

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 14.0 s 16.0 s 18.0 s 20.0 s 22.0 s 24.0 s FCP 7.4 s LCP 24.7 shttps://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2memvYaGs126MiZpBA-UvWbX... https://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2 — 42.0 KiB — 7 ms — font-display: swaphttps://fonts.gstatic.com/s/materialsymbolsrounded/v330/sykO-zNym6YjUruM-QrEh7-nyTnjDwKNJ_190FjpZIvLgyidOK7BDB_Qb9vUdV6_gjDK-P1Ju0XXkRzDgw.woff2sykO-zNym6YjUruM-QrEh7-... https://fonts.gstatic.com/s/materialsymbolsrounded/v330/sykO-zNym6YjUruM-QrEh7-nyTnjDwKNJ_190FjpZIvLgyidOK7BDB_Qb9vUdV6_gjDK-P1Ju0XXkRzDgw.woff2 — 1.4 MiB — 78 ms — font-display: swaphttps://fonts.gstatic.com/s/opensans/v44/memQYaGs126MiZpBA-UFUIcVXSCEkx2cmqvXlWq8tWZ0Pw86hd0Rk8ZkWVAewIMSdjE.woff2memQYaGs126MiZpBA-UFUIc... https://fonts.gstatic.com/s/opensans/v44/memQYaGs126MiZpBA-UFUIcVXSCEkx2cmqvXlWq8tWZ0Pw86hd0Rk8ZkWVAewIMSdjE.woff2 — 13.8 KiB — 10 ms — font-display: swaphttps://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/fonts/inter/Inter.woff2Inter.woff2 https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/fonts/inter/Inter.woff2 — 337.8 KiB — 702 ms — font-display: swap
memvYaGs126MiZpBA-UvWbX... woff2 swap
Size 42 KB
Load time 7 ms
Start 3.1 s
Risk FOUT — text flashes from fallback to web font
sykO-zNym6YjUruM-QrEh7-... woff2 swap
Size 1459 KB
Load time 78 ms
Start 3.1 s
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
memQYaGs126MiZpBA-UFUIc... woff2 swap
Size 14 KB
Load time 10 ms
Start 3.1 s
Risk FOUT — text flashes from fallback to web font
Inter.woff2 woff2 swap
Size 338 KB
Load time 702 ms
Start 3.2 s
Risk FOUT — text flashes from fallback to web font
  • Subset this font — over 100 KB suggests Latin Extended or full glyph coverage that most pages don't need
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 ~898 KB and ~1796 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
Network Waterfall
60 requests over 5064ms
INFO
0 ms 2.0 s 4.0 s 6.0 s 8.0 s 10.0 s 12.0 s 14.0 s 16.0 s 18.0 s 20.0 s 22.0 s 24.0 s FCP 7.4 s LCP 24.7 shttps://bris.ac.uk// https://bris.ac.uk/ — 301 — 130 B — 1.1 s — http/1.0https://www.bristol.ac.uk/www.bristol.ac.uk/ https://www.bristol.ac.uk/ — 200 — 87.7 KiB — 1.3 s — http/1.1https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/index.www_bristol_ac_uk.hHsrG.v1768494982.jseu.gw.fortiabp.forticloud.com/api/v... https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/index.www_bristol_ac_uk.hHsrG.v1768494982.js — 200 — 2.1 KiB — 731 ms — h2https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/favicons/site.webmanifestwww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/favicons/site.webmanifest — 200 — 1004 B — 616 ms — http/1.1https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/css/responsive-web-project-main-2.7.0.csswww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/css/responsive-web-project-main-2.7.0.css — 200 — 146.4 KiB — 411 ms — http/1.1https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/css/responsive-web-project-fullwidth-2.7.0.csswww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/css/responsive-web-project-fullwidth-2.7.0.css — 200 — 39.8 KiB — 801 ms — http/1.1https://app.termly.io/resource-blocker/f00d1986-fa46-46cf-a165-30f04408b1ce?autoBlock=onapp.termly.io/resource-blocker/f00d... https://app.termly.io/resource-blocker/f00d1986-fa46-46cf-a165-30f04408b1ce?autoBlock=on — 200 — 143.6 KiB — 425 ms — h3https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/css/responsive-web-project-homepage-2.7.0.csswww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/css/responsive-web-project-homepage-2.7.0.css — 200 — 6.4 KiB — 603 ms — http/1.1https://www.bristol.ac.uk/media-library/sites/homepage/images/homepage-1.jpgwww.bristol.ac.uk/media-library/sit... https://www.bristol.ac.uk/media-library/sites/homepage/images/homepage-1.jpg — 200 — 516.3 KiB — 1.5 s — http/1.1https://www.bristol.ac.uk/assets/homepage-search/1.0.4/css/app.565b7505.csswww.bristol.ac.uk/assets/homepage-s... https://www.bristol.ac.uk/assets/homepage-search/1.0.4/css/app.565b7505.css — 200 — 2.0 KiB — 612 ms — http/1.1https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/app.12148122.jswww.bristol.ac.uk/assets/homepage-s... https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/app.12148122.js — 200 — 9.8 KiB — 622 ms — http/1.1https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-vendors.a3cb5fa7.jswww.bristol.ac.uk/assets/homepage-s... https://www.bristol.ac.uk/assets/homepage-search/1.0.4/js/chunk-vendors.a3cb5fa7.js — 200 — 123.8 KiB — 622 ms — http/1.1https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/main.www_bristol_ac_uk.hHsrG.v1768494982.jseu.gw.fortiabp.forticloud.com/api/v... https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/main.www_bristol_ac_uk.hHsrG.v1768494982.js — 200 — 295.1 KiB — 1.5 s — h2https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/vendor.www_bristol_ac_uk.hHsrG.v1768494982.jseu.gw.fortiabp.forticloud.com/api/v... https://eu.gw.fortiabp.forticloud.com/api/v1/gw/static/js/vendor.www_bristol_ac_uk.hHsrG.v1768494982.js — 200 — 74.9 KiB — 1.1 s — h2https://fonts.googleapis.com/css2?family=Open+Sans:ital,wght@0,400;0,600;0,700;1,400&display=swapfonts.googleapis.com/css2?family=Op... https://fonts.googleapis.com/css2?family=Open+Sans:ital,wght@0,400;0,600;0,700;1,400&display=swap — 200 — 2.0 KiB — 132 ms — h2https://fonts.googleapis.com/css2?family=Material+Symbols+Rounded:opsz,wght,FILL,GRAD@48,100..700,0..1,0&display=swapfonts.googleapis.com/css2?family=Ma... https://fonts.googleapis.com/css2?family=Material+Symbols+Rounded:opsz,wght,FILL,GRAD@48,100..700,0..1,0&display=swap — 200 — 888 B — 131 ms — h2https://www.googletagmanager.com/gtm.js?id=GTM-MWCJ929www.googletagmanager.com/gtm.js?id=... https://www.googletagmanager.com/gtm.js?id=GTM-MWCJ929 — 200 — 194.8 KiB — 294 ms — h2https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/images/logos/uob-logo.svgwww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/images/logos/uob-logo.svg — 200 — 12.2 KiB — 204 ms — http/1.1https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-main-2.7.0.jswww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-main-2.7.0.js — 200 — 14.2 KiB — 216 ms — http/1.1https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-slider-2.7.0.jswww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-slider-2.7.0.js — 200 — 75.8 KiB — 593 ms — http/1.1https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-vimeo-2.7.0.jswww.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/js/responsive-web-project-vimeo-2.7.0.js — 200 — 38.8 KiB — 206 ms — http/1.1https://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2fonts.gstatic.com/s/opensans/v44/me... https://fonts.gstatic.com/s/opensans/v44/memvYaGs126MiZpBA-UvWbX2vVnXBbObj2OVTS-mu0SC55I.woff2 — 200 — 42.0 KiB — 7 ms — h3https://fonts.gstatic.com/s/materialsymbolsrounded/v330/sykO-zNym6YjUruM-QrEh7-nyTnjDwKNJ_190FjpZIvLgyidOK7BDB_Qb9vUdV6_gjDK-P1Ju0XXkRzDgw.woff2fonts.gstatic.com/s/materialsymbols... https://fonts.gstatic.com/s/materialsymbolsrounded/v330/sykO-zNym6YjUruM-QrEh7-nyTnjDwKNJ_190FjpZIvLgyidOK7BDB_Qb9vUdV6_gjDK-P1Ju0XXkRzDgw.woff2 — 200 — 1.4 MiB — 78 ms — h3https://fonts.gstatic.com/s/opensans/v44/memQYaGs126MiZpBA-UFUIcVXSCEkx2cmqvXlWq8tWZ0Pw86hd0Rk8ZkWVAewIMSdjE.woff2fonts.gstatic.com/s/opensans/v44/me... https://fonts.gstatic.com/s/opensans/v44/memQYaGs126MiZpBA-UFUIcVXSCEkx2cmqvXlWq8tWZ0Pw86hd0Rk8ZkWVAewIMSdjE.woff2 — 200 — 13.8 KiB — 10 ms — h3https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/fonts/inter/Inter.woff2www.bristol.ac.uk/assets/responsive... https://www.bristol.ac.uk/assets/responsive-web-project/2.7.0/fonts/inter/Inter.woff2 — 200 — 337.8 KiB — 702 ms — http/1.1data:image/svg+xml;utf8,<svg fill='rgb(51, 51, 51)' height='24' viewBox='0 0 24 24' width='24' xmln…data:image/svg+xml;utf8,<svg fill='... data:image/svg+xml;utf8,<svg fill='rgb(51, 51, 51)' height='24' viewBox='0 0 24 24' width='24' xmln… — 200 — 0 B — 0 ms — 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HTML JavaScript CSS Images Fonts XHR/Fetch Other
Third-Party Script Cost
Per-script blocking time, transfer cost, and cache headers
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Transfer 88 KB
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Unattributable
Other
Costly
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Google Tag Manager
Tag Manager
Costly
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Unused 30%
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eu.gw.fortiabp.forticloud.com
Other
Costly
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Transfer 75 KB
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app.termly.io
Other
Costly
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Transfer 144 KB
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app.termly.io
Other
Optional
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Transfer 143 KB
Unused 58%
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www.bristol.ac.uk
Other
Optional
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Transfer 14 KB
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www.bristol.ac.uk
Other
Optional
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Transfer 10 KB
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www.bristol.ac.uk
Other
Optional
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Transfer 124 KB
Unused 38%
Monthly Cost £1/mo
www.bristol.ac.uk
Other
Optional
Execution 82ms
Transfer 0 KB
Unused 69%
Monthly Cost £1/mo

These scripts may cost more than they're worth

  • www.bristol.ac.uk adds 1753ms and costs ~£18/month
  • Unattributable adds 1205ms and costs ~£12/month
  • Google Tag Manager adds 633ms and costs ~£7/month
  • eu.gw.fortiabp.forticloud.com adds 612ms and costs ~£6/month
  • app.termly.io adds 486ms and costs ~£5/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.bristol.ac.uk takes 1753ms 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 1205ms 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 633ms 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

eu.gw.fortiabp.forticloud.com takes 612ms 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

57% of eu.gw.fortiabp.forticloud.com'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

app.termly.io takes 486ms 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

58% of app.termly.io'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

69% of www.bristol.ac.uk'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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