PrestaShop 9 themes target evergreen browsers, browsers that update automatically and stay current. This means modern versions, not a specific pinned release. The minimum floor is set by Bootstrap 5.3, which the entire theme stack is built on.
Web Platform Baseline is a signal created by browser vendors (Google, Mozilla, Apple, Microsoft) that tells you when a web feature is safe to use across all major browsers. PrestaShop 9 themes use it as the reference for deciding whether a CSS or JavaScript feature can be used without fallbacks.
Baseline divides features into three tiers:
| Tier | Definition | Usage |
|---|---|---|
| Widely Available | Supported in all major browsers for 30+ months | Use freely, no fallback needed |
| Newly Available | Just reached cross-browser support | Use with care, consider your audience’s browser update frequency |
| Limited availability | Not yet supported in all major browsers | Avoid, or use only with a @supports fallback |
You can check any feature’s Baseline status on MDN (shown in the browser compatibility table) or caniuse.com.
For features that are Newly Available or where you want to gracefully degrade, use @supports:
/* Base layout: works everywhere */
.product-list {
display: grid;
grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
}
/* Container queries: Newly Available, @supports guards older browsers */
@supports (container-type: inline-size) {
.product-list {
container-type: inline-size;
}
@container (max-width: 400px) {
.product-card {
flex-direction: column;
}
}
}
Test your theme in modern versions of all supported browsers before release: