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.
1.87 s
Largest Contentful Paint Largest Contentful Paint — how long until the largest visible element loads. Under 2.5s is good.
2.24 s
Total Blocking Time Total Blocking Time — total time the main thread was blocked, preventing user input. Under 200ms is good.
92 ms
Cumulative Layout Shift Cumulative Layout Shift — measures visual stability. How much the page layout shifts during loading. Under 0.1 is good.
0.012
Speed Index Speed Index — how quickly content is visually displayed during load. Under 3.4s is good.
2.18 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.
3.84 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 sDThird-Party ImpactAction100% third-party, 0 ms blockingFIX
DPage Weight InventoryAction127 resources · 1.9 MB · 238 KB savings availableFIX
~238.2 KiB of savings available
| # | Resource | Type | Size | Cache | Unused | 3rd party | Issues |
|---|---|---|---|---|---|---|---|
| — | — | ||||||
| 127 resources | 1.9 MiB | ||||||
FHTTP CachingActionNo cache headersFIX
No Cache-Control header
Adding a Cache-Control header can significantly improve repeat-visit performance.
CPage Weight BudgetAction1.9 MB transferred, 127 requestsREVIEW
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
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
BImage Optimization17 images, 0 KB saveableREVIEW
CJS Execution CostAction1319ms total JS executionREVIEW
Main Thread Breakdown
| Script | Total | Scripting | Parse/Compile | Party |
|---|---|---|---|---|
| https://www.iisd.org/ | 320ms | 23ms | 1ms | 3rd |
| Unattributable | 222ms | 6ms | 0ms | 3rd |
| https://www.googletagmanager.com/gtag/js?id=G-F1MTSXWF9Y&cx=c>m=4e64k0h1 | 123ms | 100ms | 22ms | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T3RMTW | 116ms | 96ms | 19ms | 3rd |
| https://www.iisd.org/cdn-cgi/challenge-platform/scripts/jsd/main.js | 105ms | 100ms | 1ms | 3rd |
| https://scripts.clarity.ms/0.8.60-beta/clarity.js | 101ms | 78ms | 4ms | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-876050736&cx=c>m=4e64k0h1 | 92ms | 73ms | 18ms | 3rd |
| https://kit.fontawesome.com/0db7d48973.js | 89ms | 86ms | 1ms | 3rd |
| https://www.iisd.org/core/assets/vendor/jquery/jquery.min.js?v=3.7.1 | 80ms | 39ms | 3ms | 3rd |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 70ms | 58ms | 10ms | 3rd |
CJS BundlesAction34 scripts, 238 KB unusedREVIEW
Downloaded but never executed on this page.
| Script | Size | Unused | Minified | Party |
|---|---|---|---|---|
| https://www.googletagmanager.com/gtag/js?id=G-F1MTSXWF9Y&cx=c>m=4e64k0h1 | 177 KB | 70 KB (39%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtag/destination?id=AW-876050736&cx=c>m=4e64k0h1 | 144 KB | 67 KB (46%) | ✓ | 3rd |
| https://www.googletagmanager.com/gtm.js?id=GTM-T3RMTW | 155 KB | 65 KB (42%) | ✓ | 3rd |
| https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js | 57 KB | 36 KB (65%) | ✓ | 3rd |
| https://cdnjs.cloudflare.com/ajax/libs/jquery.perfect-scrollbar/1.4.0/perfect-scrollbar.min.js | 5 KB | — | ✓ | 3rd |
| https://cdnjs.cloudflare.com/ajax/libs/magnific-popup.js/1.1.0/jquery.magnific-popup.min.js | 7 KB | — | ✓ | 3rd |
| https://www.iisd.org/core/assets/vendor/js-cookie/js.cookie.min.js?v=3.0.5 | 1 KB | — | ✓ | 3rd |
| https://www.iisd.org/modules/contrib/eu_cookie_compliance/js/eu_cookie_compliance.min.js?v=10.4.7 | 6 KB | — | ✓ | 3rd |
| https://www.iisd.org/themes/custom/iisd/assets/js/featured-box.js?td6ux8 | 2 KB | — | ✓ | 3rd |
| https://www.iisd.org/themes/custom/iisd/assets/js/header-social.js?td6ux8 | 1 KB | — | ✓ | 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
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
No green hosting detected
A+Text CompressionAll text resources are compressedPASS
A+Font Loading3 fonts (42 KB)PASS
Web fonts
3
42 KB total
Render-blocking
0
of 3
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
Network Waterfall127 requests over 3242msINFO
Third-Party Script CostPer-script blocking time, transfer cost, and cache headersINFO
| Script | Category | Execution | Transfer | Unused | Monthly Cost | Verdict |
|---|---|---|---|---|---|---|
www.iisd.org www.iisd.org | Other | 320ms | 20 KB | — | €3/mo | Costly |
Unattributable Unattributable | Other | 222ms | 0 KB | — | €2/mo | Costly |
Google Tag Manager www.googletagmanager.com | Tag Manager | 123ms | 177 KB | 39% | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 116ms | 155 KB | 42% | €1/mo | Optional |
www.iisd.org www.iisd.org | Other | 105ms | 0 KB | — | €1/mo | Optional |
Microsoft Clarity scripts.clarity.ms | Session Replay | 101ms | 25 KB | — | €1/mo | Optional |
Google Tag Manager www.googletagmanager.com | Tag Manager | 92ms | 144 KB | 46% | €1/mo | Optional |
kit.fontawesome.com kit.fontawesome.com | Other | 89ms | 6 KB | — | €1/mo | Optional |
www.iisd.org www.iisd.org | Other | 80ms | 31 KB | — | €1/mo | Optional |
Hotjar script.hotjar.com | Session Replay | 70ms | 57 KB | 65% | €1/mo | Optional |
These scripts may cost more than they're worth
- www.iisd.org adds 320ms and costs ~€3/month
- Unattributable adds 222ms and costs ~€2/month
100% of JavaScript execution time is spent on third-party scripts. Consider auditing which scripts are essential.
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.iisd.org takes 320ms 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
Unattributable takes 222ms 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
65% 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