Performance
· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.Performance-focused optimization plan with CWV assessment, top offenders, and time estimates
First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.
902 ms
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
3.28 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
159 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.287
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
2.35 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.
7.92 s
Page Load Progression
732 ms
1.5 s
2.2 s
2.9 s
3.7 s
4.4 s
5.1 s
5.9 sFPage Weight BudgetAction19.4 MB transferred, 170 requestsFIX
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.
Source: web.dev
Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.
JavaScript bundle is large — code-split routes and lazy-load off-screen components to defer.
Source: web.dev
Remove unused CSS rules with tools like PurgeCSS to reduce stylesheet size.
CSS bundle is large — purge unused styles (PurgeCSS, Tailwind JIT) to reduce CSS payload.
Source: web.dev
Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.
High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.
Source: web.dev
FJS BundlesAction42 scripts, 908 KB unusedFIX
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-HTQ6N1C1EK&cx=c>m=4e64k0 | 173 KB | 70 KB (40%) | ✓ | 3rd |
| https://cdn.curator.io/5.0/curator.embed.js | 103 KB | 64 KB (63%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-958583275&cx=c>m=4e64k0 | 144 KB | 62 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-17497736984&cx=c>m=4e64k0 | 144 KB | 62 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-943473154&cx=c>m=4e64k0 | 143 KB | 62 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-465216367&cx=c>m=4e64k0 | 144 KB | 62 KB (43%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-14248141&cx=c>m=4e64k0 | 129 KB | 61 KB (47%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-4768938&cx=c>m=4e64k0 | 129 KB | 61 KB (47%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-4743369&cx=c>m=4e64k0 | 129 KB | 61 KB (47%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/js?id=DC-13730620&cx=c>m=4e64k0 | 132 KB | 61 KB (46%) | ✓ | 3rd |
Consider code splitting or tree shaking to reduce unused code.
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.
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.
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.
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.
This bundle has high unused code — code-split or tree-shake to ship only what executes.
Source: web.dev / Lighthouse coverage
FPage Weight InventoryAction170 resources · 19.4 MB · 908 KB savings availableFIX
~907.6 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 170 resources | 19.4 MiB | ||||||
BImage Optimization76 images, 0 KB saveableREVIEW
CJS Execution CostAction1872ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://dur.ac.uk/ | 436ms | 6ms | 1ms | 1st |
| Unattributable | 273ms | 10ms | 0ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-MD895GR | 224ms | 186ms | 29ms | 3rd |
| https://cdn.curator.io/5.0/curator.embed.js | 157ms | 101ms | 7ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-17497736984&cx=c>m=4e64k0 | 96ms | 74ms | 8ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-HTQ6N1C1EK&cx=c>m=4e64k0 | 86ms | 74ms | 10ms | 3rd |
| https://dur.ac.uk/media/durham-university/site-assets/js/dependencies-20231018.js | 76ms | 35ms | 7ms | 1st |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 70ms | 59ms | 6ms | 3rd |
| https://scripts.clarity.ms/0.8.60-beta/clarity.js | 65ms | 54ms | 2ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=AW-465216367&cx=c>m=4e64k0 | 64ms | 57ms | 7ms | 3rd |
Showing top 10 of 16 scripts
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
AThird-Party Impact26% third-party, 0 ms blockingPASS
A+Text CompressionAll text resources are compressedPASS
A+Font Loading6 fonts (107 KB)PASS
Web fonts
6
107 KB total
Render-blocking
0
of 6
Dominant font-display
swap
Most common across fonts
Font loading timeline
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 CachingAll resources properly cachedPASS
A+Critical Rendering PathNo render-blocking resourcesPASS
A+Resource HintsNo optimization neededPASS
AHTTP Cachingmax-age=172800 (2 days)PASS
max-age=172800
| Directive | Value | Meaning |
|---|---|---|
| max-age | 172800 | Cache for 2 days |
Network Waterfall170 requests over 5575msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
Unattributable Unattributable | Other | 273ms | 0 KB | — | £3/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 224ms | 190 KB | 23% | £2/mo | Costly |
cdn.curator.io cdn.curator.io | Other | 157ms | 103 KB | 63% | £2/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 96ms | 144 KB | 43% | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 86ms | 173 KB | 40% | £1/mo | Optional |
Hotjar script.hotjar.com | Session Replay | 70ms | 57 KB | 67% | £1/mo | Optional |
Microsoft Clarity scripts.clarity.ms | Session Replay | 65ms | 25 KB | — | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 64ms | 144 KB | 43% | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 60ms | 144 KB | 43% | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 59ms | 143 KB | 43% | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 53ms | 129 KB | 44% | £1/mo | Optional |
code.jquery.com code.jquery.com | Other | 50ms | 31 KB | — | £1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 50ms | 132 KB | 46% | £1/mo | Optional |
These scripts may cost more than they're worth
- Unattributable adds 273ms and costs ~£3/month
- Google Tag Manager adds 224ms and costs ~£2/month
70% of JavaScript execution time comes from third-party scripts.
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
Unattributable takes 273ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
Google Tag Manager takes 224ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.
This script has high main-thread execution time — optimize hot paths or defer.
Source: web.dev
63% of cdn.curator.io's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev
67% of Hotjar's code is unused. The script may be loading features you don't use.
Bundle has high unused-code ratio — tree-shaking and route-splitting recover the wasted bytes.
Source: web.dev