Mycelium
Mycelium is a Squarespace theme by Squarespace (Free). Tested on 2026-10-28 with Google Lighthouse via PageSpeed Insights on its own demo store, it scores 51 for mobile speed and 75 for desktop speed, 92/92 for SEO and 96/96 for accessibility (mobile/desktop, 0–100). Note: its demo home page is heavy — 8.5 MB — heavier than a typical store, so the speed score may understate the theme.
Mobile51
Desktop75
Scores
| Mobile | Desktop | |
|---|---|---|
| Speed | 51 | 75 |
| SEO | 92 | 92 |
| Accessibility | 96 | 96 |
| Best practices | 100 | 100 |
Single preset · measured 8 times since 2026-10-14 · Lighthouse via PageSpeed Insights · 0–100, 90+ is good.
Why not 100 — Mycelium home page
Mobile
Speed 51 · 49 points to gain
- −25 Largest Contentful Paint medium effort
- −10 First Contentful Paint medium effort
- −8.8 Speed Index medium effort
- −4.8 Total Blocking Time medium effort
- 4.3 s Reduce unused JavaScript high effort
- 600 ms Reduce unused CSS high effort
SEO 92 · 8 points to gain
- −7.7 Document does not have a meta description low effort
Accessibility 96 · 4 points to gain
- −3.8 Background and foreground colors do not have a sufficient contrast ratio. medium effort
Desktop
Speed 75 · 25 points to gain
- −18.8 Largest Contentful Paint medium effort
- −2.6 Speed Index medium effort
- −2.1 Total Blocking Time medium effort
- −1.4 First Contentful Paint medium effort
- 720 ms Reduce unused JavaScript high effort
- 120 ms Reduce unused CSS high effort
SEO 92 · 8 points to gain
- −7.7 Document does not have a meta description low effort
Accessibility 96 · 4 points to gain
- −3.8 Background and foreground colors do not have a sufficient contrast ratio. medium effort
Presets and pages
| Preset / page | Speed | SEO | A11y | Speed | SEO | A11y | Tested |
|---|---|---|---|---|---|---|---|
| mobile | desktop | ||||||
| Mycelium default demo ↗ | 51 | 92 | 96 | 75 | 92 | 96 | 2026-10-28 |
| home ↗ | 51 | 92 | 96 | 75 | 92 | 96 | 2026-10-28 |
Show this score on your site
A live badge: it always shows Mycelium's current score and links back here. Paste this where the theme is sold or documented.
<a href="https://themestested.com/theme/squarespace/mycelium-fluid-demo"><img src="https://themestested.com/badge/squarespace/mycelium-fluid-demo.svg" alt="Mycelium speed score on Themestested" height="20"></a>
Add ?device=d for the desktop score, or ?metric=seo / ?metric=a11y for SEO or accessibility.