Software

    

The iPhone 6 line ships pre-loaded with iOS 8, while the iPhone 5S shipped pre-loaded with iOS 7. Apps are able to take advantage of the increased screen size in the iPhone 6 and 6 Plus to display more information on-screen; for example, the Mail app uses a dual-pane layout similar to its iPad version when the device is in landscape mode on the iPhone 6 Plus. As it uses an identical aspect ratio, apps designed for the iPhone 5, 5C, and 5S can be upscaled for use on the iPhone 6 and 6 Plus. To improve the usability of the devices' larger screens, an additional "Reachability" gesture was added; double-touching the Home button will slide the top half of the screen's contents down to the bottom half of the screen. This function allows users to reach buttons located near the top of the screen, such as a "Back" button in the top-left corner.

Both iPhone 6 models have received generally positive reviews. Re/code called it "the best smartphone you can buy". TechRadar praised the iPhone 6's "brilliant" design, improved battery life over the 5S, iOS 8 for being "smarter and more intuitive than ever", along with the quality of its camera. However, the plastic antenna strips on the rear of the phone were criticized for resulting in poor aesthetics, the display for having lower resolution and pixel density in comparison to other recent smartphones - including those with the same physical screen size as the iPhone 6, such as the HTC One, and for not having a sufficient justification for its significantly higher price in comparison to similar devices running Android or Windows Phone.

The Verge considered the iPhone 6 to be "simply and cleanly designed" in comparison to the 5S, noting that the phone still felt usable despite its larger size, but criticized the antenna plastic, the protruding camera lens (which prevents the device from sitting flat without a case), and the lack of additional optimization in the operating system for the bigger screen. Improvements such as performance, battery life, VoLTE support, and other tweaks were also noted. In conclusion, the iPhone 6 was considered "good, even great, but there’s little about it that’s truly ambitious or truly moving the needle. It’s just a refinement of a lot of existing ideas into a much more pleasant package".

In regards to the 6 Plus, Engadget panned the device's design for feeling uncomfortable to hold and harder to grip in comparison to other devices such as the Galaxy Note 3 and LG G3, but praised its inclusion of optical image stabilization and slightly better battery life than the 6.

Chassis bending

Shortly after its public release, it was reported that the iPhone 6 Plus chassis was susceptible to bending under pressure, such as when carried tightly in a user's pocket. While such issues are not exclusive to the iPhone 6 Plus, the design flaw came to be known among social media users as "bendgate." A study by Consumer Reports found the iPhone 6 and 6 Plus were slightly more durable than the HTC One, but considerably less durable than the other phones tested.
Apple responded to the bending allegations, stating that they had only received nine complaints of bent devices, and that the damage occurring due to regular use is "extremely rare." The company maintained that the iPhone 6 and 6 Plus went through durability testing to ensure they would stand up to daily use.The company offered to replace phones that were bent, if it is determined that the bending was unintentional.

On October 1, 2014, it was reported by Axel Telzerowm, editor-in-chief of the German technology magazine Computer Bild, that following the posting of a video where a presenter was able to bend an iPhone 6 Plus, an Apple Germany representative informed the publication that it had been banned from future Apple events and that it would no longer receive devices directly from Apple for testing. Telzerowm responded by saying that "we congratulate you to your fine new generation of iPhones, even if one of them has a minor weakness with its casing. But we are deeply disappointed about the lack of respect of your company."

Hair ripping

On October 3, 2014 9to5Mac released a post claiming that certain iPhone 6 and iPhone 6 Plus users complained on social networking sites that the phone ripped off their hair when they held the phone close to their ears when making a call or taking a call.This second design flaw was given the term "hairgate." Twitter users claimed that the seam between the glass screen and aluminium back of the iPhone 6 is to blame, with hair becoming caught within it.

Flash storage performance

Some users reported that 64 and 128 GB iPhone 6 models had experienced performance issues, and that some 128 GB iPhone 6 Plus models would, in rare cases, randomly crash and reboot. Business Korea reported that the issues were connected to the triple-layer cell NAND storage of the affected models. Triple-layer cells can store three bits of data per cell of flash, and are cheaper than dual-layer cell solutions, but at the cost of performance. It was reported that Apple had planned to switch the affected model lines back to multi-layer cell flash, and address the performance issues on existing devices in a future iOS update.

Optical image stabilization issues

It was reported that the optical image stabilization systems on some iPhone 6 Plus models were faulty, failing to properly stabilize when the phone is being held perfectly still, leading to blurry photos and "wavy"-looking videos.The optical image stabilization system was also found to have been affected by accessories that use magnets, such as third-party lens attachments; Apple issued advisories to users and its licensed accessory makers, warning that magnetic or metallic accessories can cause the OIS system to malfunction.

Sales

Apple Inc. announced that within 24 hours of availability, over 4 million pre-orders of the iPhone 6 and 6 Plus were made, exceeding the supply available. More than 10 million iPhone 6 and iPhone 6 Plus devices were sold in the first three days.