speedrun.a16z.com/demo-day

The numbers

First visit

0.291 g CO₂e

Return visit

0.0044 g CO₂e

Hosting

unknown

LCP

1.26 s

CLS

n/a

TTFB

6 ms

At 10,000 views a month this page emits about 26.3 kg CO₂e a year, roughly 108 km in an average petrol car. The estimate assumes 75% new and 25% returning visitors, a measured cache reload ratio of 2%, and world-average grid intensity. How we calculate this

1. Reduce JavaScript payloadsave ~0.033 g/visit (294 kB)High impact · moderate effort

   13 scripts total 1.18 MB on the wire (4.12 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.

   • _app-96134cb456a3216c.js680 kB
   • js170 kB
   • gtm.js131 kB
   • framework-74a4a8727fd84a0c.js102 kB
   • main-c654606de7e303fa.js42 kB

   WSG 3.2: Minify and remove unused codeWSG 3.3: Modularize bandwidth-heavy components
2. Serve images at the size they displaysave ~0.032 g/visit (287 kB)Medium impact · quick fix

   2 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.

   • image234 kB
   • image176 kB

   WSG 2.9: Optimize media to reduce resource use
3. Audit third-party servicessave ~0.017 g/visit (152 kB)Medium impact · moderate effort

   5 third-party domains account for 303 kB (15% 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.

   • www.googletagmanager.com300 kB
   • cdn.sanity.io2.3 kB
   • region1.google-analytics.com559 B
   • o66518.ingest.us.sentry.io281 B
   • 0 B

   WSG 3.5: Treat third parties the same as first parties
4. 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
5. Optimize web fontssave ~0.0086 g/visit (77 kB)Advisory · quick fix

   6 font files total 220 kB.

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

   • 64c1c31384189284-s.p.woff237 kB
   • 3d660e1dc7b780d4-s.p.woff237 kB
   • 8eb8b7822da4764a-s.p.woff237 kB
   • dc72bb61e9fdf7fa-s.p.woff237 kB
   • c062731b6932ef63-s.p.woff236 kB

   WSG 2.11: Use optimized web typography
6. Remove references to broken resourcessave ~<0.001 g/visit (201 B)Advisory · quick fix

   1 request 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.

   • meHTTP 401 · 201 B

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

   At 1.96 MB per view this page rates D. 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

Where the bytes are

• JavaScript1.18 MB · 13 req
• Images438 kB · 7 req
• Fonts220 kB · 6 req
• Other70 kB · 11 req
• CSS28 kB · 1 req
• Data (fetch)21 kB · 9 req
• HTML9.9 kB · 1 req