Some sites that contain videos on the page start playing them as soon as you open them. How can I turn this off?
On Mac, there are two ways to quickly change the auto-play video preferences on sites in the standard Safari browser.
Set parameters for the current site!

1. Open a site with autoplay video.
2. On the menu bar, click Safari – Preferences for this website.
3. In the Autoplay section, specify the appropriate option: always, never, or only for files without sound.
Set parameters for all sites!

You can set general settings for all visited pages.
1. Go to Safari – Preferences – Websites.
2. Select the Autoplay section.
3. You can configure separate rules for each site or delete the rules set and configure the autoplay option for all visited pages.