Mozilla's Firefox browser will soon block ad trackers by default.

The change is intended to improve browser performance and stop online marketing firms from harvesting your data without your knowledge. "Users have the same expectations of privacy on the web, and yet in reality, they are tracked wherever they go," Mozilla VP Nick Nguyen wrote in a blog post.

In November, Mozilla added "Tracking Protection" to Firefox, which stops ads, plugins, and share buttons from collecting metadata about your online browsing activities; it arrived on iOS in April. However, outside the iOS version, the feature has been opt-in and somewhat hidden in the browser's preferences page. Prior to this, Tracking Protection was only available in Firefox's private browsing mode.

Mozilla told PCMag it intends on using some of the technology from the Tracking Protection feature to power three new default functions that'll be arriving to Firefox in the coming months. The first focuses on stopping "slow-loading" third-party trackers that can drag down Firefox's performance. The company has been testing it; if all goes well, it will be turned on in Firefox 63, which is scheduled for an October release.

The second feature is designed to stop ad trackers from following your internet presence from site to site. "In order to help give users the private web browsing experience they expect and deserve, Firefox will strip cookies and block storage access from third-party tracking content," Nguyen said. This default feature will arrive in Firefox 65, which is scheduled to release in January.

Mozilla is also working on another initiative to stop website trackers that can "fingerprint" your internet presence by identifying your computer's properties, such as the IP address and browser version. The same initiative will work on blocking websites from secretly loading cryptocurrrency miners.

Mozilla wants the changes to force websites to be more transparent about data-harvesting practices. "Some sites will continue to want user data in exchange for content, but now they will have to ask for it, a positive change for people who up until now had no idea of the value exchange they were asked to make," Nguyen said.

Mozilla's push to crack down on ad tracking won't win fans from online advertisers. But it isn't the only browser maker trying to address online privacy. In June, Apple also announced that the company's Safari browser would block plugins from third-party websites such as Facebook from tracking your activities across the internet.

Consumers can actually begin to use some of the upcoming Firefox features by downloading the "Nightly" experimental build of the browser. Turn on the features by going to the preferences icon in the menu bar, and scrolling down to a new "Content Blocking" section.

Editor's note: This story has been updated with further comment from Mozilla.