What this page costs.
We announce a carbon budget, measure it, and put it on the page. No greenwashing, no yearly average — the real footprint, per view.
We use the Sustainable Web Design (SWD) v3 simplified model: 0.81 kWh per gigabyte transferred, times the global average grid intensity (442 gCO₂e / kWh). That works out to ≈ 358 gCO₂e per gigabyte, or 3.33 × 10⁻⁷ gCO₂e per byte.
We measure server-side at build time: the sum of gzip chunks actually loaded by each page. It's conservative (we assume everything is served cold, no browser cache).
Measured in your browser right now — fetching each route + linked assets, summing bytes, converting via the SWD v3 coefficient (3.33 × 10⁻⁷ gCO₂e / byte).
Our target is ≤ 0.20 gCO₂e per view (specs §7.2). Real values sit in the section above — measured in your browser, not estimated by a third party.
For context, the 2024 web page median transfers ≈ 2.5 MB (HTTP Archive), roughly 0.83 gCO₂e per view — about four times our target.
The budget is enforced in CI: on every PR, the `Performance` workflow runs `scripts/measure-carbon.ts`, which gzips the home chunks and exits 1 over 0.20 g. See `.github/workflows/perf.yml`.
The SWD model only covers the use phase (network + device + datacenter). We don't measure — for now — manufacturing of visitor devices, nor server hardware amortisation. Our estimate is therefore a floor.
To go further: assets cached aggressively, dynamic imports systematic, dark mode by default (OLED savings), zero video autoplay. It's all documented in specs §7.