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Performance

· 15 checks — Lighthouse + waterfall + sustainability rolled into one auditable list.
SCORE
73
GRADE
C
FIX
4
REVIEW
3
PASS
6
INFO
2

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

Mobile Desktop
57
Performance Overall performance score (0–100) based on Core Web Vitals and other metrics. 90+ is good.
71
Accessibility Measures how accessible the page is for users with disabilities. Checks color contrast, ARIA labels, and semantic HTML.
100
Best Practices Checks for modern web development best practices including HTTPS, no console errors, and secure JavaScript.
83
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.

1.50 s

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

3.29 s

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

0 ms

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

0.303

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

2.43 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.

3.31 s

Page Load Progression

381 ms
762 ms
1.1 s
1.5 s
1.9 s
2.3 s
2.7 s
3.0 s
Checks
15
6 PASS 3 REVIEW 4 FIX
F
Page Weight Budget
Action
5.1 MB transferred, 38 requests
FIX
5.1 MB transferred, 38 requests
Critical::
Page weighs 5.9 MB (5.1 MB transferred)
Warning::
Images are 4.4 MB — compress or use modern formats
Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.
Got: 4.4 MB
Info::
Fonts are 272 KB — consider subsetting or using system fonts
Subset fonts to include only used characters, or switch to system font stacks.
Got: 272 KB
Info::
38 HTTP requests
Info::
Estimated 1.1 g CO2 per page load
5.1 MB / 2.4 MB budget
5.1 MB transferred
38 requests
1.1 g CO2 per page load
Images 4.4 MiB 87%
JavaScript 277.4 KiB 5%
Fonts 271.6 KiB 5%
CSS 92.3 KiB 2%
HTML 32.2 KiB 1%
Other 17.4 KiB 0%
Other 346 B 0%
0 2.4 MB 4.9 MB
Over budget

Convert images to WebP/AVIF and resize to display dimensions to reduce transfer size.

Why this matters

Image bandwidth is high — modern formats (WebP/AVIF) and resizing typically cut it 50%+.

Source: web.dev

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

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 (5.1 MiB of 5.1 MiB)
Info::
Third-party blocking time is low (0 ms)
100%
First-party Third-party
D
Page Weight Inventory
Action
38 resources · 5.1 MB · 184 KB savings available
FIX
38 resources · 5.1 MB · 184 KB savings available
Warning::
Page weight 4.1 MB over 1MB target
Got: 5.1 MB Expected: ≤ 1 MB
Info::
~184 KB of savings available
Warning::
37 third-party resources (100% of weight)
Info::
10 resources over 200KB
38 resources · 5.1 MiB · 37 third-party 4.1 MiB over 1MB target
Image 87% · 4.4 MiB
JavaScript 5% · 277.4 KiB
Font 5% · 271.6 KiB
CSS 2% · 92.3 KiB
Document 1% · 32.7 KiB

~183.8 KiB of savings available

Remove unused JavaScript: 183.8 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
Image Optimization
Action
22 images, 0 KB saveable
REVIEW
22 images, 0 KB saveable
Warning::
https://cdn.eso.org/images/banner1920/eso2520a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2519a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/videos/small169/cs0027a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/small169/annlang26004a-... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.eso.org/public/archives/static/frontpa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.eso.org/public/archives/static/frontpa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/_DSC7159-CC.... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2518a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/small169/annlang26005a-... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.eso.org/public/archives/static/frontpa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2605a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2604a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2603a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/small169/potw2616a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/small169/potw2615a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/thumb350x/2018_04_17_es... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/thumb350x/eso50_obs_com... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2517a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2521a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://www.eso.org/public/archives/static/frontpa... is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
Warning::
https://cdn.eso.org/images/banner1920/eso2601a.jpg is missing width/height — may cause layout shift
Set explicit width and height to prevent CLS.
22 images 4.4 MB
0 oversized -0 KB
22 legacy format
21 missing dimensions CLS risk

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

Set explicit width and height to prevent CLS.

Why this matters

Image without explicit width/height — browser can't reserve space; CLS jumps when image loads.

Source: web.dev / Core Web Vitals

C
JS Bundles
Action
5 scripts, 184 KB unused
REVIEW
5 scripts, 184 KB unused
Warning::
https://www.eso.org/public/archives/djp/js/main.bf...: 145 KB unused (75%)
Consider code splitting or tree shaking to reduce unused code.
Warning::
https://www.eso.org/mtmo/matomo.js: 38 KB unused (58%)
Consider code splitting or tree shaking to reduce unused code.
Info::
Total unused JavaScript: 184 KB
184 KB unused JavaScript

Downloaded but never executed on this page.

ScriptSizeUnusedMinifiedParty
https://www.eso.org/public/archives/djp/js/main.bf52206884ae.js195 KB145 KB (75%)✓3rd
https://www.eso.org/mtmo/matomo.js66 KB38 KB (58%)✓3rd
https://www.eso.org/public/archives/djp/js/main_privacy.11c2900c4c46.js2 KB—✓3rd
https://www.youtube.com/iframe_api4 KB—✓3rd
https://www.youtube.com/s/player/1bb6ee63/www-widgetapi.vflset/www-widgetapi.js11 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

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+
JS Execution Cost
476ms total JS execution
PASS
476ms total JS execution
Info::
https://www.eso.org/public/: 248ms CPU time
Info::
https://www.eso.org/public/archives/djp/js/main.bf...: 125ms CPU time
Info::
Unattributable: 103ms CPU time
Warning::
Third-party scripts: 476ms (100% of total)

Main Thread Breakdown

Other 34% Style & Layout 30% Script Evaluation 20% Script Parsing & Compilation 5% Rendering 5% Parse HTML & CSS 5%
ScriptTotalScriptingParse/CompileParty
https://www.eso.org/public/248ms1ms4ms3rd
https://www.eso.org/public/archives/djp/js/main.bf52206884ae.js125ms82ms19ms3rd
Unattributable103ms3ms0ms3rd
A+
Font Loading
4 fonts (272 KB)
PASS
4 fonts (272 KB)
Info::
4 font(s) use font-display: swap (FOUT risk but functional)

Web fonts

4

272 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 1.0 s 2.0 s 3.0 s FCP 1.5 s LCP 3.3 shttps://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2d16374c2-cd72-48c0-9623... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2 — 41.7 KiB — 480 ms — font-display: swaphttps://www.eso.org/public/archives/djp/font-awesome/webfonts/fa-solid-900.d5e647388e24.woff2fa-solid-900.d5e647388e... https://www.eso.org/public/archives/djp/font-awesome/webfonts/fa-solid-900.d5e647388e24.woff2 — 146.9 KiB — 478 ms — font-display: swaphttps://www.eso.org/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-4822-b8d2-3e344f383a70.9437aea92626.woff205c8135e-5d0b-4822-b8d2... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-4822-b8d2-3e344f383a70.9437aea92626.woff2 — 41.2 KiB — 628 ms — font-display: swaphttps://www.eso.org/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-4601-aa0b-39a06fc7a8dc.2e5dd68dc88d.woff21b94cf39-0593-4601-aa0b... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-4601-aa0b-39a06fc7a8dc.2e5dd68dc88d.woff2 — 41.8 KiB — 649 ms — font-display: swap
d16374c2-cd72-48c0-9623... woff2 swap
Size 42 KB
Load time 480 ms
Start 1.7 s
Risk FOUT — text flashes from fallback to web font
fa-solid-900.d5e647388e... woff2 swap
Size 147 KB
Load time 478 ms
Start 1.7 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
05c8135e-5d0b-4822-b8d2... woff2 swap
Size 41 KB
Load time 628 ms
Start 1.7 s
Risk FOUT — text flashes from fallback to web font
1b94cf39-0593-4601-aa0b... woff2 swap
Size 42 KB
Load time 649 ms
Start 1.7 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)

Fixing the unchecked items could save ~73 KB and ~146 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
Network Waterfall
38 requests over 3208ms
INFO
0 ms 1.0 s 2.0 s 3.0 s FCP 1.5 s LCP 3.3 shttps://eso.org// https://eso.org/ — 302 — 250 B — 557 ms — http/1.1https://www.eso.org/public/www.eso.org/public/ https://www.eso.org/public/ — 200 — 32.2 KiB — 715 ms — http/1.1https://fast.fonts.net/t/1.css?apiType=css&projectid=03892b9b-79f6-4f01-9746-af912ebf5e47fast.fonts.net/t/1.css?apiType=css&... https://fast.fonts.net/t/1.css?apiType=css&projectid=03892b9b-79f6-4f01-9746-af912ebf5e47 — 200 — 636 B — 40 ms — h2https://www.eso.org/public/archives/djp/css/main.01d86ad5297f.csswww.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/main.01d86ad5297f.css — 200 — 77.7 KiB — 514 ms — http/1.1https://cdn.eso.org/videos/small169/cs0027a.jpgcdn.eso.org/videos/small169/cs0027a... https://cdn.eso.org/videos/small169/cs0027a.jpg — 200 — 94.7 KiB — 214 ms — h2https://cdn.eso.org/images/small169/annlang26005a-es-cl.jpgcdn.eso.org/images/small169/annlang... https://cdn.eso.org/images/small169/annlang26005a-es-cl.jpg — 200 — 275.4 KiB — 260 ms — h2https://cdn.eso.org/images/small169/potw2616a.jpgcdn.eso.org/images/small169/potw261... https://cdn.eso.org/images/small169/potw2616a.jpg — 200 — 346.6 KiB — 269 ms — h2https://cdn.eso.org/images/small169/potw2615a.jpgcdn.eso.org/images/small169/potw261... https://cdn.eso.org/images/small169/potw2615a.jpg — 200 — 81.0 KiB — 235 ms — h2https://cdn.eso.org/images/small169/annlang26004a-es-cl.jpgcdn.eso.org/images/small169/annlang... https://cdn.eso.org/images/small169/annlang26004a-es-cl.jpg — 200 — 59.5 KiB — 228 ms — h2https://www.eso.org/public/archives/static/frontpage/elt.jpgwww.eso.org/public/archives/static/... https://www.eso.org/public/archives/static/frontpage/elt.jpg — 200 — 117.8 KiB — 1.0 s — http/1.1https://www.eso.org/public/archives/static/frontpage/alma.jpgwww.eso.org/public/archives/static/... https://www.eso.org/public/archives/static/frontpage/alma.jpg — 200 — 254.2 KiB — 1.2 s — http/1.1https://www.eso.org/public/archives/static/frontpage/vlt.jpgwww.eso.org/public/archives/static/... https://www.eso.org/public/archives/static/frontpage/vlt.jpg — 200 — 211.6 KiB — 1.2 s — http/1.1https://www.eso.org/public/archives/static/frontpage/lasilla.jpgwww.eso.org/public/archives/static/... https://www.eso.org/public/archives/static/frontpage/lasilla.jpg — 200 — 138.7 KiB — 1.1 s — http/1.1https://cdn.eso.org/images/thumb350x/2018_04_17_es_moon-venus_4-cc.jpgcdn.eso.org/images/thumb350x/2018_0... https://cdn.eso.org/images/thumb350x/2018_04_17_es_moon-venus_4-cc.jpg — 200 — 18.7 KiB — 234 ms — h2https://www.eso.org/public/archives/djp/css/extras.d3e54451ebbb.csswww.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/extras.d3e54451ebbb.css — 200 — 13.9 KiB — 537 ms — http/1.1https://cdn.eso.org/images/thumb350x/eso50_obs_compo.jpgcdn.eso.org/images/thumb350x/eso50_... https://cdn.eso.org/images/thumb350x/eso50_obs_compo.jpg — 200 — 23.0 KiB — 35 ms — h2https://www.eso.org/public/archives/djp/js/main.bf52206884ae.jswww.eso.org/public/archives/djp/js/... https://www.eso.org/public/archives/djp/js/main.bf52206884ae.js — 200 — 195.0 KiB — 368 ms — http/1.1https://www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.pngwww.eso.org/public/archives/djp/spr... https://www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.png — 200 — 87.6 KiB — 669 ms — http/1.1https://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2www.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2 — 200 — 41.7 KiB — 480 ms — http/1.1https://www.eso.org/public/archives/djp/font-awesome/webfonts/fa-solid-900.d5e647388e24.woff2www.eso.org/public/archives/djp/fon... https://www.eso.org/public/archives/djp/font-awesome/webfonts/fa-solid-900.d5e647388e24.woff2 — 200 — 146.9 KiB — 478 ms — http/1.1https://www.eso.org/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-4822-b8d2-3e344f383a70.9437aea92626.woff2www.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/05c8135e-5d0b-4822-b8d2-3e344f383a70.9437aea92626.woff2 — 200 — 41.2 KiB — 628 ms — http/1.1https://www.eso.org/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-4601-aa0b-39a06fc7a8dc.2e5dd68dc88d.woff2www.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/1b94cf39-0593-4601-aa0b-39a06fc7a8dc.2e5dd68dc88d.woff2 — 200 — 41.8 KiB — 649 ms — http/1.1https://www.eso.org/public/archives/djp/js/main_privacy.11c2900c4c46.jswww.eso.org/public/archives/djp/js/... https://www.eso.org/public/archives/djp/js/main_privacy.11c2900c4c46.js — 200 — 2.1 KiB — 300 ms — http/1.1https://www.youtube.com/iframe_apiwww.youtube.com/iframe_api https://www.youtube.com/iframe_api — 200 — 3.5 KiB — 26 ms — h2https://cdn.eso.org/images/banner1920/eso2517a.jpgcdn.eso.org/images/banner1920/eso25... https://cdn.eso.org/images/banner1920/eso2517a.jpg — 200 — 195.1 KiB — 17 ms — h2https://cdn.eso.org/images/banner1920/eso2605a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2605a.jpg — 200 — 236.2 KiB — 26 ms — h2https://www.youtube.com/s/player/1bb6ee63/www-widgetapi.vflset/www-widgetapi.jswww.youtube.com/s/player/1bb6ee63/w... https://www.youtube.com/s/player/1bb6ee63/www-widgetapi.vflset/www-widgetapi.js — 200 — 10.6 KiB — 7 ms — h2https://cdn.eso.org/images/banner1920/eso2604a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2604a.jpg — 200 — 161.7 KiB — 16 ms — h2https://cdn.eso.org/images/banner1920/eso2603a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2603a.jpg — 200 — 608.2 KiB — 54 ms — h2https://cdn.eso.org/images/banner1920/_DSC7159-CC.jpgcdn.eso.org/images/banner1920/_DSC7... https://cdn.eso.org/images/banner1920/_DSC7159-CC.jpg — 200 — 346.3 KiB — 36 ms — h2
0 ms 1.0 s 2.0 s 3.0 s FCP 1.5 s LCP 3.3 shttps://eso.org// https://eso.org/ — 302 — 250 B — 557 ms — http/1.1https://www.eso.org/public/www.eso.org/public/ https://www.eso.org/public/ — 200 — 32.2 KiB — 715 ms — http/1.1https://fast.fonts.net/t/1.css?apiType=css&projectid=03892b9b-79f6-4f01-9746-af912ebf5e47fast.fonts.net/t/1.css?apiType=css&... https://fast.fonts.net/t/1.css?apiType=css&projectid=03892b9b-79f6-4f01-9746-af912ebf5e47 — 200 — 636 B — 40 ms — h2https://www.eso.org/public/archives/djp/css/main.01d86ad5297f.csswww.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/main.01d86ad5297f.css — 200 — 77.7 KiB — 514 ms — http/1.1https://cdn.eso.org/videos/small169/cs0027a.jpgcdn.eso.org/videos/small169/cs0027a... https://cdn.eso.org/videos/small169/cs0027a.jpg — 200 — 94.7 KiB — 214 ms — h2https://cdn.eso.org/images/small169/annlang26005a-es-cl.jpgcdn.eso.org/images/small169/annlang... https://cdn.eso.org/images/small169/annlang26005a-es-cl.jpg — 200 — 275.4 KiB — 260 ms — h2https://cdn.eso.org/images/small169/potw2616a.jpgcdn.eso.org/images/small169/potw261... https://cdn.eso.org/images/small169/potw2616a.jpg — 200 — 346.6 KiB — 269 ms — h2https://cdn.eso.org/images/small169/potw2615a.jpgcdn.eso.org/images/small169/potw261... https://cdn.eso.org/images/small169/potw2615a.jpg — 200 — 81.0 KiB — 235 ms — h2https://cdn.eso.org/images/small169/annlang26004a-es-cl.jpgcdn.eso.org/images/small169/annlang... https://cdn.eso.org/images/small169/annlang26004a-es-cl.jpg — 200 — 59.5 KiB — 228 ms — h2https://www.eso.org/public/archives/static/frontpage/elt.jpgwww.eso.org/public/archives/static/... https://www.eso.org/public/archives/static/frontpage/elt.jpg — 200 — 117.8 KiB — 1.0 s — http/1.1https://www.eso.org/public/archives/static/frontpage/alma.jpgwww.eso.org/public/archives/static/... https://www.eso.org/public/archives/static/frontpage/alma.jpg — 200 — 254.2 KiB — 1.2 s — 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35 ms — h2https://www.eso.org/public/archives/djp/js/main.bf52206884ae.jswww.eso.org/public/archives/djp/js/... https://www.eso.org/public/archives/djp/js/main.bf52206884ae.js — 200 — 195.0 KiB — 368 ms — http/1.1https://www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.pngwww.eso.org/public/archives/djp/spr... https://www.eso.org/public/archives/djp/sprites/sprites.73991e10bd47.png — 200 — 87.6 KiB — 669 ms — http/1.1https://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2www.eso.org/public/archives/djp/css... https://www.eso.org/public/archives/djp/css/fonts/fonts.com/d16374c2-cd72-48c0-9623-5aadd349654e.6debdb366391.woff2 — 200 — 41.7 KiB — 480 ms — http/1.1https://www.eso.org/public/archives/djp/font-awesome/webfonts/fa-solid-900.d5e647388e24.woff2www.eso.org/public/archives/djp/fon... https://www.eso.org/public/archives/djp/font-awesome/webfonts/fa-solid-900.d5e647388e24.woff2 — 200 — 146.9 KiB — 478 ms — 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h2https://cdn.eso.org/images/banner1920/eso2517a.jpgcdn.eso.org/images/banner1920/eso25... https://cdn.eso.org/images/banner1920/eso2517a.jpg — 200 — 195.1 KiB — 17 ms — h2https://cdn.eso.org/images/banner1920/eso2605a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2605a.jpg — 200 — 236.2 KiB — 26 ms — h2https://www.youtube.com/s/player/1bb6ee63/www-widgetapi.vflset/www-widgetapi.jswww.youtube.com/s/player/1bb6ee63/w... https://www.youtube.com/s/player/1bb6ee63/www-widgetapi.vflset/www-widgetapi.js — 200 — 10.6 KiB — 7 ms — h2https://cdn.eso.org/images/banner1920/eso2604a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2604a.jpg — 200 — 161.7 KiB — 16 ms — h2https://cdn.eso.org/images/banner1920/eso2603a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2603a.jpg — 200 — 608.2 KiB — 54 ms — h2https://cdn.eso.org/images/banner1920/_DSC7159-CC.jpgcdn.eso.org/images/banner1920/_DSC7... https://cdn.eso.org/images/banner1920/_DSC7159-CC.jpg — 200 — 346.3 KiB — 36 ms — h2https://cdn.eso.org/images/banner1920/eso2601a.jpgcdn.eso.org/images/banner1920/eso26... https://cdn.eso.org/images/banner1920/eso2601a.jpg — 200 — 128.4 KiB — 23 ms — h2https://cdn.eso.org/images/banner1920/eso2521a.jpgcdn.eso.org/images/banner1920/eso25... https://cdn.eso.org/images/banner1920/eso2521a.jpg — 200 — 341.3 KiB — 32 ms — h2https://cdn.eso.org/images/banner1920/eso2520a.jpgcdn.eso.org/images/banner1920/eso25... https://cdn.eso.org/images/banner1920/eso2520a.jpg — 200 — 64.6 KiB — 7 ms — h2https://cdn.eso.org/images/banner1920/eso2519a.jpgcdn.eso.org/images/banner1920/eso25... https://cdn.eso.org/images/banner1920/eso2519a.jpg — 200 — 214.7 KiB — 21 ms — h2https://cdn.eso.org/images/banner1920/eso2518a.jpgcdn.eso.org/images/banner1920/eso25... https://cdn.eso.org/images/banner1920/eso2518a.jpg — 200 — 506.4 KiB — 45 ms — h2https://www.eso.org/mtmo/matomo.jswww.eso.org/mtmo/matomo.js 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https://www.eso.org/mtmo/matomo.php?action_name=ESO&idsite=1&rec=1&r=955989&h=21&m=5&s=38&url=https%3A%2F%2Fwww.eso.org%2Fpublic%2F&_id=&_idn=1&send_image=0&_refts=0&pv_id=AVlPYk&pf_net=360&pf_srv=182&pf_tfr=174&pf_dm1=1286&pf_dm2=360&pf_onl=6&uadata=%7B%22formFactors%22%3A%5B%22Desktop%22%5D%2C%22fullVersionList%22%3A%5B%7B%22brand%22%3A%22Not-A.Brand%22%2C%22version%22%3A%2224.0.0.0%22%7D%2C%7B%22brand%22%3A%22Chromium%22%2C%22version%22%3A%22146.0.7680.164%22%7D%5D%2C%22mobile%22%3Afalse%2C%22model%22%3A%22%22%2C%22platform%22%3A%22macOS%22%2C%22platformVersion%22%3A%2210.15.7%22%7D&pdf=1&qt=0&realp=0&wma=0&fla=0&java=0&ag=0&cookie=1&res=800x600 — 204 — 346 B — 244 ms — http/1.1
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 476ms · 227KB · €2/mo
www.eso.org
Other
Costly
Execution 248ms
Transfer 32 KB
Monthly Cost €1/mo
www.eso.org
Other
Optional
Execution 125ms
Transfer 195 KB
Unused 75%
Monthly Cost €1/mo
Unattributable
Other
Optional
Execution 103ms
Transfer 0 KB
Monthly Cost €0/mo

These scripts may cost more than they're worth

  • www.eso.org adds 248ms and costs ~€1/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.eso.org takes 248ms 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

75% of www.eso.org'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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