Image: Mozilla

Mozilla’s Firefox browser version 93 has arrived, and its main new feature is tab offloading.

Currently only available on Windows, with macOS and Linux to follow, the feature starts when the browser thinks an out-of-memory crash is imminent, and it will unload tabs with the least recently used unloaded first. Tabs that are in the foreground are never unloaded with tabs pinned, using picture-in-picture or playing sound are less likely to be unloaded.

On Windows, the threshold is around the 6% mark, Mozilla engineer Haik Aftandilian wrote in a blog post.

“We have experimented with offloading tabs on Windows in the past, but one problem we couldn’t overcome was balancing less browser memory usage with user boredom. because there is a slight delay when the tab is reloaded, is rather difficult exercise, and we have never achieved satisfactory results, “said Aftandilian.

“We have approached the problem again by fine-tuning our low memory detection and tab selection algorithm and limiting the action to the case where we are sure to provide a benefit to the user: if the browser is on the point to crash. ”

A month of testing on Firefox’s Nightly channel revealed a decrease in browser crashes and content processing, but also an increase in out of memory crashes, as well as an increase in average memory usage.

“The latter may seem very counterintuitive, but is easily explained through survival … browser sessions that had such high memory usage would have crashed and burned in the past, but are now able to survive by unloading. tabs just before pressing the critical threshold, ”said the engineer.

“The increase in OOM crashes, also very counter-intuitive, is more difficult to explain.

“We are working to improve our understanding of this issue and the relevant heuristics. But given the clearly improved results for users, we felt it was unnecessary to retain the functionality.”

In the next version of Firefox, an about: unloads page will be added to provide diagnostics on tab unloading.

Firefox 93 also includes a feature to block HTTP downloads from HTTPS pages, followed by displaying a dialog box warning users that this is a potential security risk and asking them to they want to continue as well as block downloads from sandboxed iframes, unless they have permission. -downloads attribute.

The browser has also ended the default support for 3DES encryption, but it will still be available when sites use outdated TLS versions.

“Recent measurements indicate that Firefox is encountering servers that choose to use 3DES about as often as servers that use outdated versions of TLS,” Mozilla said.

“As long as 3DES remains an option provided by Firefox, it poses a security and privacy risk. Because it is no longer necessary or safe to use this encryption algorithm, it is disabled by default in Firefox 93.”

Firefox 93 also packs the third version of its SmartBlock technology, which can replace Google Analytics, Optimizely, Criteo, Amazon TAM, and various Google ad javascript with local versions that behave like the originals enough to keep sites from crashing.

The browser changes its SEO policy to ensure that sites cannot override the default split that Firefox applies to cross-site URLs. The same site requests will continue to pass the full referral URL.

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