Apple knows what is causing the new MacBook Pro's battery woes.

A couple weeks after Consumer Reports failed to recommend the latest MacBook Pro due to inconsistent battery life, Apple has announced that it worked with the publication to identify the problem: a bug in Safari. However, if you are experiencing poor battery life with your new machine, don't assume you have the bug as well, because apparently, this is a problem mostly specific to Consumer Reports.

When Consumer Reports recently experienced low and wildly inconsistent battery results on the upgraded laptops during testing, Apple stood by its advertised battery claims. But it has now discovered the results were due to a software bug that occurs in Safari’s developer mode. It affected Consumer Reports’ test, which “uses a hidden Safari setting for developing web sites which turns off the browser cache".

Apple noted most consumers don't use this setting and therefore shouldn't be impacted by the bug - nor should they be experiencing variable battery life in general. Still, after it finally found something to blame, Apple asked Consumer Reports to run the same test using normal user settings, and the publication told Apple that its MacBook Pro systems "consistently delivered the expected battery life".

Here is Apple's full statement on the matter, which an Apple spokesperson gave to Pocket-lint: 

"We appreciate the opportunity to work with Consumer Reports over the holidays to understand their battery test results. We learned that when testing battery life on Mac notebooks, Consumer Reports uses a hidden Safari setting for developing web sites which turns off the browser cache. This is not a setting used by customers and does not reflect real-world usage. Their use of this developer setting also triggered an obscure and intermittent bug reloading icons which created inconsistent results in their lab. After we asked Consumer Reports to run the same test using normal user settings, they told us their MacBook Pro systems consistently delivered the expected battery life. We have also fixed the bug uncovered in this test. This is the best pro notebook we’ve ever made, we respect Consumer Reports and we’re glad they decided to revisit their findings on the MacBook Pro"

So, Apple is releasing a software patch. The update, which will root out the Safari bug going forward, is available to those in the Apple Beta Software program. It will be also part of a broader update released in a few weeks. Consumer Reports said it will conduct another round of battery life tests with the update installed. It will also recommend the new MacBook Pros if the battery problem is resolved.

The publication explained that it had disabled caching in Safari for consistent testing across platforms. But keep in mind Pocket-lint also noticed reduced battery life of around 10 hours (compared to 12 for last year's model), and we tested the machine with normal settings.

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