In a major nod to privacy, new versions of Mozilla’s Firefox web browser will, by default, block third-party companies from tracking the online behavior of users, Mozilla said Thursday.
Although many popular web browsers like Google (goog) Chrome and Microsoft’s (msft) Internet Explorer include options for limiting the amount of data companies can collect, users must manually activate those settings. Mozilla, in contrast, said it would turn the ability off, which means that users would specifically have to turn it back on again to be tracked.
Mozilla said in a blog post that “many of the harms of unchecked data collection are completely opaque to users and experts alike” and then cited a news story about Facebook’s Cambridge Analytica scandal as an example of a data privacy blunder. Facebook (fb) faced fierce criticism from lawmakers over its failure to safeguard user data from the Cambridge Analytica political consulting firm, which obtained people’s Facebook data from an academic researcher who had collected it in violation of Facebook’s lax policies.
Mozilla’s decision to emphasize “by default” is noteworthy considering privacy advocates and some politicians criticize companies like Facebook and Google for making it difficult for users to find and change the data privacy settings in their products.
This spring, during a congressional hearing about Facebook’s recent data privacy mishaps, New Jersey Rep. Frank Pallone asked Facebook CEO Mark Zuckerberg whether the company would alter its default privacy settings to minimize data collection. Zuckerberg responded without committing, saying that “this is a complex issue that deserves more than a one-word answer.”
Mozilla also said that its efforts to reduce data that third parties can collect through its browser would also combat a data-collection technique called “fingerprinting.” With this technique, Mozilla said, companies can “invisibly identify users” via certain attributes and internal settings of their devices, which people cannot control.
Upcoming versions of Firefox will also prevent websites from silently injecting software code into users’ computers that secretly diverts computing resources to mine cryptocurrency.
Mozilla did not elaborate on how it plans to block the various data-collection schemes it mentioned in its post, or give a specific date for when its anti data-collection practices will start.
Get Data Sheet, Fortune’s technology newsletter.
According to website analytics firm StatCounter, Google Chrome is the most popular web browser, representing nearly 60% of the world’s total browser market as of July. Apple’s Safari browser has 14% of the market, followed by the Chinese web browser UC Browser (developed by Alibaba Group), which has 7%.
Firefox is the fourth most popular web browser with 5% of the market, followed by the Opera Browser and Microsoft’s Internet Explorer, which have 3.4% and 3% of the market, respectively.