# Mobile-First Indexing — SEO for Developers
Source: https://www.geekswithgeeks.com/en/seo-developers/seo-mobile-first
> Understand that Google now indexes the mobile version of your site first and evaluates it for ranking.
## Mobile-first is the default
Since 2018, Google crawls and indexes the *mobile* version of your site first. Desktop version is secondary. If your mobile site is slower, has missing content, or poor UX, your rankings suffer — regardless of desktop quality.
## Responsive design example
Use responsive CSS to make your site work on all screen sizes. Use the viewport meta tag and CSS media queries.
```html
Mobile-Friendly Content
```