Wow, that sounds very annoying. Sometimes advertisers use the '''Flash''' player plugin. You can change a setting so that Flash doesn't run on a site without your approval. If you okay videos on NY Times, that also would apply to the ads, so it's not perfect. But maybe it will help somewhat. Here's how: Open the '''Add-ons page''' using either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click '''Plugins'''. On the right side, look for "Shockwave Flash" and change "Always Activate" to "Ask to Activate". With this setting, when you visit a site that wants to use Flash, you should see a notification icon in the address bar and usually (but not always) one of the following: a link in a black rectangle in the page or an infobar sliding down between the toolbar area and the page. The plugin notification icon in the address bar typically looks like a small, dark gray Lego block. When the page wants to use a blocked plugin, the icon turns red to alert you to the concern. If you see a good reason to use Flash, and the site looks trustworthy, you can go ahead and click the notification icon in the address bar to allow Flash. You can trust the site for the time being or permanently. But some pages use Flash only for tracking or playing ads, so if you don't see an immediate need for Flash, feel free to ignore the notification! It will just sit there in case you want to use it later. If you want finer control, this extension would resolve the issue of only wanting ''some'' videos on a page to play: https://addons.mozilla.org/firefox/addon/click-to-play-per-element/ (I haven't tried it myself) ---- Some advertisers might use the built-in '''HTML5 video''' player instead of Flash. There is a hidden setting to turn off autoplay. Unfortunately, sites have figured out a workaround, which is to wait and then sent a play command to the player after it loads. Firefox doesn't yet block that trick. If you want to try the current setting for those sites where it works: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter. Click the button promising to be careful. (2) In the search box above the list, type or paste '''media''' and pause while the list is filtered (3) Double-click the '''media.autoplay.enabled''' preference to switch it from true to false.