Most vulnerabilities in modern computer systems are patched without any noticeable impact for end users. That’s not necessarily the case with Meltdown and Spectre, which strike at the very heart of microprocessors functionality. A new round of Spectre flaws have appeared, but Google is in the process of adding functionality to desktop Chrome that will block remote execution of Spectre. The downside, however, is Chrome will use even more RAM than it already does.

Spectre targets a feature of microprocessors called speculative execution, which performs calculations that may be needed ahead of time. This increases overall system performance dramatically, but it also opens the door to attacks that can read data in memory that is supposed to remain private. Rolling out patches for both Spectre and Meltdown has been a complicated process, some of which can impact system performance.

Google v67 build of Chrome contains a feature called Site Isolation to combat Spectre attacks. This feature has been available in Chrome since v63, but it was behind a developer flag. Now, it’s on by default for everyone. Site Isolation makes Spectre attacks less dangerous by using a separate renderer for each domain. Chrome has always had a multi-process architecture separated by tabs, but a single tab could render content from multiple domains by way of cross-site iframes or clever JavaScript. That setup could theoretically allow a Spectre exploit to read data belonging to other domains on the page, like your passwords or browser cookies.

Enforcing Site Isolation comes with a drawback, though. Using a separate renderer for every domain means more active renderers, and thus, more memory usage. Chrome is already notorious for high RAM usage, but it could be 10-13 percent higher with Site Isolation enabled. This feature already rolled out in the beta and dev channels, so some of you have experienced the effects.

While this feature has rolled out widely, Google says about 1 percent of desktop Chrome users still won’t have Site Isolation right away. Google is holding that group back so it can test the effects and make sure the change is working correctly. They’ll get Site Isolation later if everything goes as planned. The Android version of Chrome has Site Isolation later because of the different OS concerns. It will be an option in v68, though. The iOS version of Chrome runs on Apple’s rendering engine because of platform restrictions, so Google can’t make any rendering changes there.