Apple is showing Adobe Flash the door in Safari 10.

When the next-gen browser ships this fall with macOS Sierra, Flash will be deactivated by default. Sites that have HTML5 and Flash will go with HTML5. But for sites without HTML5 that require Flash, Apple will display a pop-up that gives users the option to install it.

“When that’s clicked, Safari offers the user the options of activating the plug-in just one time or every time the user visits that website. Here too, the default option is to activate the plug-in only once,” Ricky Mondello from Apple’s Safari team wrote in a blog post(Opens in a new window).

The new policy applies across the Web; there is no built-in list of exceptions. If a website requires a legacy plug-in, users can manually activate it on that page.

“If you’re a Web developer, you should be aware of how this change will affect your users’ experiences if parts of your websites rely on legacy plug-ins,” Mondello said.

He urged developers to test how the upcoming changes will impact their sites by installing a beta of macOS Sierra; betas of Safari 10 for OS X Yosemite and OS X El Capitan are coming later this summer.

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Cupertino, during a security presentation at WWDC this week, also announced(Opens in a new window) plans to require all iOS apps to connect to the Internet via HTTPS by Jan. 1, 2017.

Last month, Google announced that later this year, HTML5 will become the “primary experience” on Chrome, if a website offers it. As of Sept. 1, Chrome automatically pauses many Flash ads by default to improve user performance.

In April, Microsoft said its Edge browser will automatically pause certain kinds of Flash content while you’re browsing the Web. Firefox blocks some versions(Opens in a new window)of Flash—mostly older ones.