github.com

The numbers

First visit

0.701 g CO₂e

Return visit

<0.001 g CO₂e

Hosting

unknown

LCP

532 ms

CLS

0.059

TTFB

7 ms

At 10,000 views a month this page emits about 63.1 kg CO₂e a year, roughly 259 km in an average petrol car. The estimate assumes 75% new and 25% returning visitors, a measured cache reload ratio of 0%, and world-average grid intensity. How we calculate this

1. Audit third-party servicessave ~0.256 g/visit (2.30 MB)High impact · moderate effort

   2 third-party domains account for 4.61 MB (97% 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.

   • github.githubassets.com3.90 MB
   • images.ctfassets.net701 kB

   WSG 3.5: Treat third parties the same as first parties
2. Reduce JavaScript payloadsave ~0.048 g/visit (432 kB)High impact · moderate effort

   96 scripts total 1.73 MB on the wire (7.37 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.

   • landing-pages-1032f3d024937bed.js482 kB
   • primer-react-9fd99fd6e2426d74.js136 kB
   • 47166-2b46d439e854f735.js107 kB
   • react-core-cf2029c980a9134b.js81 kB
   • behaviors-8b278a81bec0e9d2.js59 kB

   WSG 3.2: Minify and remove unused codeWSG 3.3: Modularize bandwidth-heavy components
3. Serve images at the size they displaysave ~0.039 g/visit (350 kB)High impact · quick fix

   7 images are encoded at more than twice the pixels the layout shows, even accounting for this viewport's pixel density.

   Generate multiple sizes and let the browser pick with srcset/sizes; a 4000px original behind a 400px slot spends bandwidth no screen displays.

   • accordion-2-730955545f07.webp214 kB
   • accordion-3-52ca331d22ea.webp192 kB
   • accordion-1-ce487d44c0bf.webp167 kB
   • accordion-4-a26744b70ff7.webp123 kB
   • particles-170bd1fd231f4669.png35 kB

   WSG 2.9: Optimize media to reduce resource use
4. Convert and compress imagessave ~0.029 g/visit (262 kB)Medium impact · quick fix

   12 images (583 kB) ship in legacy formats (JPEG/PNG/GIF).

   Serve AVIF (or WebP) with responsive srcset sizes, and re-compress oversized files. AVIF typically halves JPEG weight at the same visual quality.

   • head_sss-b7e053d8d541a414.jpg194 kB
   • head_sss-29270cf59da664ea.jpg143 kB
   • mascot-7c495cf9822e0d5c.jpg45 kB
   • body_sss-ecb11ff73d84fd3b.jpg42 kB
   • particles-170bd1fd231f4669.png35 kB

   WSG 2.9: Optimize media to reduce resource use
5. Optimize web fontssave ~0.019 g/visit (167 kB)Medium impact · quick fix

   3 font files total 477 kB.

   Subset fonts to used glyphs, prefer one variable font over multiple weights, serve WOFF2 only, and consider system fonts for UI text.

   • MonaSansVF-wdth-wght-opsz-7a868ff47c93bd97.woff2220 kB
   • MonaSansVF-wdth-wght-opsz-902d64c7ad02.woff2220 kB
   • MonaSansMonoVF-wght-da74d51ce1316829.woff238 kB

   WSG 2.11: Use optimized web typography
6. Defer video and audioMedium impact · quick fix

   2 videos preload data without preload="none".

   Never autoload media: use preload="none" with a poster image, load players on interaction, and stream in an efficient codec (AV1/HEVC).

   • code-1_desktop-6d44c7cb53b4aebb.mp40 B

   WSG 2.9: Optimize media to reduce resource use
7. Verify your hosting energyMedium impact · moderate effort

   This host has not published renewable energy evidence with the Green Web Foundation, so its energy source is unknown.

   Choose a provider listed in the Green Web Directory, or ask your current provider to publish evidence (and a carbon.txt). This cuts the data-center share of every single page view.

   • carbon.txtNo carbon.txt found at the site root; publishing one is the lightest first step.

   WSG 4.1: Use sustainable hosting
8. Upgrade compression beyond gzipsave ~0.0021 g/visit (19 kB)Advisory · quick fix

   127 kB of text ships gzip-compressed; Brotli or Zstandard would cut roughly another 15-20%, and browsers without them fall back to gzip automatically.

   Serve precompressed Brotli for static text assets (highest level, compressed at build time) and enable Brotli or zstd for dynamic responses; keep gzip only as the fallback.

   • github.com122 kB
   • logo-duolingo-14477f9e54a6.svg3.3 kB
   • logo-gartner-aa8c2e452b64.svg1.8 kB

   WSG 4.3: Reduce data transfer with compression
9. Set a page-weight budgetAdvisory · moderate effort

   At 4.73 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
10. Simplify the document structureAdvisory · larger effort

    The page renders 1776 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

Where the bytes are

• JavaScript1.73 MB · 96 req
• Images1.28 MB · 18 req
• Data (fetch)826 kB · 4 req
• Fonts477 kB · 3 req
• CSS289 kB · 24 req
• HTML122 kB · 1 req
• Other497 B · 2 req
• Audio / video0 B · 1 req

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