www.youtube.com

The numbers

First visit

0.480 g CO₂e

Return visit

0.062 g CO₂e

Hosting

verified green

LCP

1.81 s

CLS

0.024

TTFB

118 ms

At 10,000 views a month this page emits about 45.1 kg CO₂e a year, roughly 185 km in an average petrol car. The estimate assumes 75% new and 25% returning visitors, a measured cache reload ratio of 13%, and world-average grid intensity. How we calculate this

1. Reduce JavaScript payloadsave ~0.070 g/visit (740 kB)High impact · moderate effort

   17 scripts total 2.96 MB on the wire (13.81 MB decoded). Bundles this size usually carry a lot of unused code.

   Split bundles per route, tree-shake dependencies, and audit with a bundle analyzer or coverage profile. A 25% cut is a conservative target for bundles this size.

   • m=kevlar_base_module,kevlar_main_module,kevla…2.12 MB
   • base.js688 kB
   • remote.js35 kB
   • vZ8OtzlOv62X1f-3i1Z4TdQc_ftzUyIFb01ru5dGZgg.js24 kB
   • offline.js23 kB

   WSG 3.2: Minify and remove unused codeWSG 3.3: Modularize bandwidth-heavy components
2. Enable text compressionsave ~0.026 g/visit (270 kB)High impact · quick fix

   3 text resources (386 kB) are served without gzip/Brotli.

   Enable Brotli (or at least gzip) on the server or CDN for HTML, CSS, JavaScript, JSON and SVG. Typical reduction is ~70%.

   • json;base64,eyJyZXNwb25zZUNvbnRleHQiOnsic2Vyd…263 kB
   • ZXhwaXJlPTE2OTcyNjc2NTQmc291cmNlPXlvdXR1YmUmc…62 kB
   • ZXhwaXJlPTE2OTcyNjc2NTQmc291cmNlPXlvdXR1YmUmc…62 kB

   WSG 4.3: Reduce data transfer with compression
3. Audit third-party servicessave ~0.019 g/visit (197 kB)High impact · moderate effort

   8 third-party domains account for 549 kB (14% of the page).

   Remove services that no longer earn their place; load the rest on interaction (facades for embeds, delayed consent-gated tags). Each third party is also a privacy and performance dependency.

   • 387 kB
   • fonts.gstatic.com103 kB
   • www.google.com28 kB
   • fonts.googleapis.com18 kB
   • www.gstatic.com12 kB
   • accounts.google.com1.9 kB

   WSG 3.5: Treat third parties the same as first parties
4. Remove references to broken resourcessave ~<0.001 g/visit (154 B)Advisory · quick fix

   7 requests answered 4xx/5xx on load: transfer and connections spent on nothing, on every single visit.

   Delete or fix the references (stale asset URLs, dead third-party tags). Each one is a request the page provably does not need.

   • videoplaybackHTTP 403 · 0 B
   • videoplaybackHTTP 403 · 0 B
   • feedbackHTTP 400 · 154 B
   • videoplaybackHTTP 403 · 0 B
   • videoplaybackHTTP 403 · 0 B

   WSG 4.4: Setup necessary error pages and redirection links
5. Set a page-weight budgetAdvisory · moderate effort

   At 3.97 MB per view this page rates F. The findings above list where the weight is.

   Agree a transfer budget (e.g. under 975 kB reaches a B), enforce it in CI, and re-scan after each change to hold the line.

   WSG 3.1: Set goals based on performance and energy impact
6. Remove the entry redirectAdvisory · quick fix

   The address that was scanned goes through 1 redirect before the document is served, ending at https://www.youtube.com/. Every hop is a full round trip on a connection that has not warmed up yet.

   Point links, sitemaps and canonical tags at the final address, and make the host redirect in one hop rather than chaining http to https to www.

   • https://youtube.com/redirects to https://www.youtube.com/

   WSG 4.4: Setup necessary error pages and redirection links
7. Simplify the document structureAdvisory · larger effort

   The page renders 2992 DOM elements, above the 1,500 guideline. Large trees cost memory and CPU on every visitor's device.

   Flatten wrapper markup, render long lists virtually or paginate, and prefer semantic elements over nested divs.

   WSG 3.6: Ensure code follows good semantic practices
8. Upgrade connections to HTTP/2 or HTTP/3Advisory · quick fix

   1 host serves five or more resources over HTTP/1.1, paying per-request connection and header overhead newer protocols eliminate.

   Enable HTTP/2 (or HTTP/3) on the server or move the assets behind a CDN that speaks it; multiplexing makes many small requests nearly free.

   • rr5---sn-q4fl6nd6.googlevideo.com6 requests over http/1.1

   WSG 3.1: Set goals based on performance and energy impact

Where the bytes are

• JavaScript2.96 MB · 17 req
• Other387 kB · 6 req
• CSS370 kB · 8 req
• HTML103 kB · 2 req
• Fonts76 kB · 2 req
• Data (fetch)40 kB · 105 req
• Audio / video26 kB · 4 req
• Images3.6 kB · 2 req
• Data (XHR)202 B · 2 req