Carbon report
www.mozilla.org/en-US
Scanned · all pages on www.mozilla.org
Redirected here by the site from mozilla.org
0.069 g
cleaner than an estimated 91.2% of pages on the web
- A+
- A
- B
- C
- D
- E
- F
A+ is 0.04 g or less per view, F is more than 0.359 g CO₂e.
The numbers
- 0.092 g CO₂e
- <0.001 g CO₂e
- verified green
- 640 ms
- 0.001
- 8 ms
At 10,000 views a month this page emits about 8.3 kg CO₂e a year, roughly 34 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
What to fix
apply everything → ~0.049 g/visit, rating A
Convert and compress imagessave ~0.015 g/visit (169 kB)Medium impact · quick fix
8 images (376 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.
- download.2e16d0ba.fill-600x600.png108 kB
- showcase-som-2025.width-1376.png56 kB
- donate.2e16d0ba.fill-800x400.jpg50 kB
- lamp-mobile-1450.2e16d0ba.fill-600x600.jpg47 kB
- collective-mobile-1450.2e16d0ba.fill-600x600.jpg35 kB
Reduce JavaScript payloadsave ~0.0046 g/visit (50 kB)Medium impact · moderate effort
12 scripts total 201 kB on the wire (650 kB 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.
- ui.js101 kB
- airgap.js54 kB
- sentry.729c728748fa.js21 kB
- lib.c6b4f4c6aed8.js5.9 kB
- m24-ui.a40c4b15e29f.js4.4 kB
Collapse the redirect chainMedium impact · quick fix
The address that was scanned goes through 2 redirects before the document is served, ending at https://www.mozilla.org/en-US/. 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://mozilla.org/redirects to https://www.mozilla.org/en-US/
Where the bytes are
- Images402 kB · 30 req
- JavaScript201 kB · 12 req
- Fonts110 kB · 4 req
- CSS26 kB · 6 req
- HTML22 kB · 1 req
- Data (fetch)2.5 kB · 1 req
Ten heaviest requests
| Resource | Type | Wire size | Cache-Control |
|---|---|---|---|
| www.mozilla.org/media/cms/images/download.2e16d0ba.fill-600x600.png | image | 108 kB | max-age=315360000, public, immutable |
| transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/ui.js | script | 101 kB | public, max-age=60 |
| www.mozilla.org/media/cms/images/showcase-som-2025.width-1376.png | image | 56 kB | max-age=315360000, public, immutable |
| transcend-cdn.com/cm/d556c3a1-e57c-4bdf-a490-390a1aebf6dd/airgap.js | script | 54 kB | public, max-age=60 |
| www.mozilla.org/media/cms/images/donate.2e16d0ba.fill-800x400.jpg | image | 50 kB | max-age=315360000, public, immutable |
| www.mozilla.org/media/cms/images/lamp-mobile-1450.2e16d0ba.fill-600x600.jpg | image | 47 kB | max-age=315360000, public, immutable |
| www.mozilla.org/media/cms/images/collective-mobile-1450.2e16d0ba.fill-600x600.jpg | image | 35 kB | max-age=315360000, public, immutable |
| www.mozilla.org/media/cms/images/ventures-mobile-1450_GxBP35h.2e16d0ba.fill-600x600.jpg | image | 35 kB | max-age=315360000, public, immutable |
| www.mozilla.org/media/cms/images/ecosystem-mobile-1450.2e16d0ba.fill-600x600.jpg | image | 33 kB | max-age=315360000, public, immutable |
| www.mozilla.org/media/protocol/fonts/mozilla-headline/MozillaHeadline-SemiBold.bccc6c46c123.woff2 | font | 29 kB | max-age=315360000, public, immutable |
Share this report
<a href="https://carbonless.cc/report/www.mozilla.org/en-US"><img src="https://carbonless.cc/api/badge?url=https%3A%2F%2Fwww.mozilla.org%2Fen-US" alt="Carbon rating for this page" width="150" height="30" loading="lazy" /></a>The badge is a lightweight SVG (under 1 kB) served with long-lived caching, so a new scan can take up to a day to show through.