Performance

· 17 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.

SCORE

GRADE

FIX

REVIEW

PASS

INFO

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

Mobile Desktop

Performance

100

Accessibility

Best Practices

SEO

First Contentful Paint First Contentful Paint — how long until the browser renders the first piece of content. Under 1.8s is good.

5.08 s

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

9.07 s

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

1.64 s

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

0.033

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

5.50 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.

14.38 s

Page Load Progression

392 ms

783 ms

1.2 s

1.6 s

2.0 s

2.4 s

2.7 s

3.1 s

Checks

7 PASS 4 REVIEW 4 FIX

Third-Party Impact

Action

100% third-party, 0 ms blocking

FIX

100% third-party, 0 ms blocking

Third-party code accounts for 100% of page weight (1.5 MiB of 1.5 MiB)

Third-party blocking time is low (0 ms)

100%

First-party Third-party

JS Execution Cost

Action

5665ms total JS execution

FIX

5665ms total JS execution

https://www.iisd.org/: 934ms CPU time

https://script.hotjar.com/modules.6a0f3932cb1341a3...: 904ms CPU time

Unattributable: 850ms CPU time

https://www.googletagmanager.com/gtag/js?id=G-F1MT...: 522ms CPU time

https://www.googletagmanager.com/gtm.js?id=GTM-T3R...: 474ms CPU time

Third-party scripts: 5665ms (100% of total)

Main Thread Breakdown

Script Evaluation 60% Other 20% Style & Layout 9% Script Parsing & Compilation 6%

Script	Total	Scripting	Parse/Compile	Party
https://www.iisd.org/	934ms	83ms	5ms	3rd
https://script.hotjar.com/modules.6a0f3932cb1341a35c18.js	904ms	761ms	34ms	3rd
Unattributable	850ms	31ms	0ms	3rd
https://www.googletagmanager.com/gtag/js?id=G-F1MTSXWF9Y&cx=c&gtm=4e64k0	522ms	422ms	96ms	3rd
https://www.googletagmanager.com/gtm.js?id=GTM-T3RMTW	474ms	391ms	76ms	3rd
https://www.iisd.org/cdn-cgi/challenge-platform/scripts/jsd/main.js	433ms	410ms	5ms	3rd
https://scripts.clarity.ms/0.8.60-beta/clarity.js	362ms	278ms	12ms	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-876050736&cx=c&gtm=4e64k0	331ms	260ms	68ms	3rd
https://kit.fontawesome.com/0db7d48973.js	317ms	306ms	3ms	3rd
https://www.iisd.org/core/assets/vendor/jquery/jquery.min.js?v=3.7.1	276ms	138ms	18ms	3rd

Showing top 10 of 12 scripts

Page Weight Inventory

Action

122 resources · 1.5 MB · 226 KB savings available

FIX

122 resources · 1.5 MB · 226 KB savings available

Page weight 537 KB over 1MB target

Got: 1.5 MB Expected: ≤ 1 MB

~226 KB of savings available

121 third-party resources (100% of weight)

1 resources over 200KB

122 resources · 1.5 MiB · 121 third-party 536.5 KiB over 1MB target

JavaScript 43% · 677.7 KiB

Image 43% · 674.3 KiB

CSS 9% · 143.5 KiB

Font 3% · 42.4 KiB

Document 1% · 20.0 KiB

Other 0% · 2.6 KiB

~226.3 KiB of savings available

Remove unused JavaScript: 226.3 KiB

#	Resource	Type	Size	Cache	Unused	3rd party	Issues

122 resources			1.5 MiB

HTTP Caching

Action

No cache headers

FIX

No cache headers

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.

Page Weight Budget

1.5 MB transferred, 122 requests

REVIEW

1.5 MB transferred, 122 requests

Page weighs 3.7 MB (1.5 MB transferred)

JavaScript is 678 KB — consider code splitting or lazy loading

Large JavaScript bundles delay interactivity. Split code by route or defer non-critical scripts.

Got: 678 KB

122 HTTP requests — consider bundling or reducing

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Estimated 0.32 g CO2 per page load

1.5 MB transferred

122 requests

0.32 g CO2 per page load

JavaScript 677.7 KiB 43%

Images 648.2 KiB 42%

Other 94.5 KiB 6%

CSS 49.6 KiB 3%

Fonts 42.4 KiB 3%

Other 26.7 KiB 2%

HTML 19.9 KiB 1%

Other 1.5 KiB 0%

Other 80 B 0%

0 2.4 MB 4.9 MB

Approaching limit

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

Each request adds latency. Bundle small files, use sprites, or eliminate unnecessary requests.

Why this matters

High HTTP request count — bundling, sprite-ing, and HTTP/2 server push can reduce per-request overhead.

Source: web.dev

Image Optimization

10 images, 0 KB saveable

REVIEW

10 images, 0 KB saveable

All images are well-optimized

10 images 648 KB

0 oversized -0 KB

9 legacy format

0 missing dimensions CLS risk

JS Bundles

Action

35 scripts, 226 KB unused

REVIEW

35 scripts, 226 KB unused

https://www.googletagmanager.com/gtag/js?id=G-F1MT...: 70 KB unused (39%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtag/destination?...: 67 KB unused (46%)

Consider code splitting or tree shaking to reduce unused code.

https://www.googletagmanager.com/gtm.js?id=GTM-T3R...: 65 KB unused (42%)

Consider code splitting or tree shaking to reduce unused code.

https://script.hotjar.com/modules.6a0f3932cb1341a3...: 25 KB unused (44%)

Consider code splitting or tree shaking to reduce unused code.

Total unused JavaScript: 226 KB

226 KB unused JavaScript

Downloaded but never executed on this page.

Script	Size	Unused	Minified	Party
https://www.googletagmanager.com/gtag/js?id=G-F1MTSXWF9Y&cx=c&gtm=4e64k0	177 KB	70 KB (39%)	✓	3rd
https://www.googletagmanager.com/gtag/destination?id=AW-876050736&cx=c&gtm=4e64k0	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	25 KB (44%)	✓	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.

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

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

All text resources are properly compressed.

A+

Font Loading

3 fonts (42 KB)

PASS

3 fonts (42 KB)

3 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

42 KB total

Render-blocking

of 3

Dominant font-display

swap

Most common across fonts

Font loading timeline

Transfer FOIT (block) FOUT (swap)

3AA016_3_unhinted_0.woff2 woff2 swap

Size 14 KB

Load time 32 ms

Start 1.9 s

Risk FOUT — text flashes from fallback to web font

3AA016_6_unhinted_0.woff2 woff2 swap

Size 14 KB

Load time 36 ms

Start 1.9 s

Risk FOUT — text flashes from fallback to web font

3AA016_5_unhinted_0.woff2 woff2 swap

Size 14 KB

Load time 36 ms

Start 1.9 s

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

No caching issues found

All static resources have appropriate caching headers.

A+

Critical Rendering Path

No render-blocking resources

PASS

No render-blocking resources

No render-blocking resources detected

A+

Resource Hints

No optimization needed

PASS

No optimization needed

No resource hint issues

A+

Render-Blocking Resources

No render-blocking resources detected

PASS

No render-blocking resources detected

No render-blocking resources detected in <head>

A+

Third-Party Resources

No third-party resources detected

PASS

No third-party resources detected

Network Waterfall

122 requests over 5799ms

INFO

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 5665ms · 626KB · €62/mo

Script	Category	Execution	Transfer	Unused	Monthly Cost	Verdict
www.iisd.org www.iisd.org	Other	934ms	20 KB	—	€10/mo	Costly
Hotjar script.hotjar.com	Session Replay	904ms	57 KB	44%	€10/mo	Costly
Unattributable Unattributable	Other	850ms	0 KB	—	€9/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	522ms	177 KB	39%	€6/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	474ms	155 KB	42%	€5/mo	Costly
www.iisd.org www.iisd.org	Other	433ms	0 KB	—	€5/mo	Costly
Microsoft Clarity scripts.clarity.ms	Session Replay	362ms	25 KB	—	€4/mo	Costly
Google Tag Manager www.googletagmanager.com	Tag Manager	331ms	144 KB	46%	€4/mo	Costly
kit.fontawesome.com kit.fontawesome.com	Other	317ms	6 KB	—	€3/mo	Costly
www.iisd.org www.iisd.org	Other	276ms	31 KB	—	€3/mo	Costly
www.iisd.org www.iisd.org	Other	189ms	1 KB	—	€2/mo	Optional
static.cloudflareinsights.com static.cloudflareinsights.com	Other	76ms	11 KB	—	€1/mo	Optional

www.iisd.org

Other

Costly

Execution 934ms

Transfer 20 KB

Monthly Cost €10/mo

Hotjar

Session Replay

Costly

Execution 904ms

Transfer 57 KB

Unused 44%

Monthly Cost €10/mo

Unattributable

Other

Costly

Execution 850ms

Transfer 0 KB

Monthly Cost €9/mo

Google Tag Manager

Tag Manager

Costly

Execution 522ms

Transfer 177 KB

Unused 39%

Monthly Cost €6/mo

Google Tag Manager

Tag Manager

Costly

Execution 474ms

Transfer 155 KB

Unused 42%

Monthly Cost €5/mo

www.iisd.org

Other

Costly

Execution 433ms

Transfer 0 KB

Monthly Cost €5/mo

Microsoft Clarity

Session Replay

Costly

Execution 362ms

Transfer 25 KB

Monthly Cost €4/mo

Google Tag Manager

Tag Manager

Costly

Execution 331ms

Transfer 144 KB

Unused 46%

Monthly Cost €4/mo

kit.fontawesome.com

Other

Costly

Execution 317ms

Transfer 6 KB

Monthly Cost €3/mo

www.iisd.org

Other

Costly

Execution 276ms

Transfer 31 KB

Monthly Cost €3/mo

www.iisd.org

Other

Optional

Execution 189ms

Transfer 1 KB

Monthly Cost €2/mo

static.cloudflareinsights.com

Other

Optional

Execution 76ms

Transfer 11 KB

Monthly Cost €1/mo

These scripts may cost more than they're worth

www.iisd.org adds 934ms and costs ~€10/month
Hotjar adds 904ms and costs ~€10/month
Unattributable adds 850ms and costs ~€9/month
Google Tag Manager adds 522ms and costs ~€6/month
Google Tag Manager adds 474ms and costs ~€5/month
www.iisd.org adds 433ms and costs ~€5/month
Microsoft Clarity adds 362ms and costs ~€4/month
Google Tag Manager adds 331ms and costs ~€4/month
kit.fontawesome.com adds 317ms and costs ~€3/month
www.iisd.org adds 276ms 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.iisd.org takes 934ms of CPU time. Consider loading it asynchronously or replacing it with a lighter alternative.

Why this matters