The iPhone 6 and 6 Plus include larger 4.7-inch and 5.5-inch displays, a faster processor, upgraded cameras, improved LTE and Wi-Fi connectivity and support for a near-field communications-based mobile payments offering.

[23][24] The iPhone 6 and 6 Plus have been the subject of several hardware issues, including most prominently, being susceptible to bending under hard pressure (dubbed "Bendgate"), and as a byproduct of this lack of rigidity, the touchscreen's internal hardware being susceptible to losing its connection to the phone's logic board (nicknamed "Touch Disease").

The iPhone 5 and its immediate successors featured a display that was taller, but the same width as prior models, measuring at 4 inches diagonally.

[29][30] Reports prior to its unveiling also speculated Apple might use a new iPhone model to introduce a mobile payments platform using near-field communications—a technology that was incorporated into many Android phones, but had experienced a low adoption rate among users.

"[33][34] In August 2015, Apple initiated a replacement program for some early iPhone 6 Plus models that were found to have potentially faulty cameras that could be causing photos to appear blurry.

In February 2017, the iPhone 6 was quietly relaunched in carrier stores and online, this time the storage has been changed to 32 GB.

[50] Unlike the previous models, the rear-facing camera is not flush with the rear of the device, but instead protrudes slightly.

[21][22] However, the optical image stabilization of the iPhone 6 Plus is only available for photography and deactivated during video recording.

[55] Like the predecessor, the iPhone 6 and 6 Plus are equipped with an accelerometer, gyroscope, front-facing proximity sensor and a digital compass.

[60] 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.

[61] The Verge considered the iPhone 6 to be "simply and cleanly designed" in comparison to the 5s, noting 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.

[40] In regards to the 6 Plus, Engadget panned its design for being 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.

[62] The iPhone 6 and 6 Plus were affected by a number of notable hardware-related issues, including but not limited to concerns surrounding their rigidity (which led to incidents surrounding chassis bending, as well as degradation or outright loss of touchscreen functionality), performance issues on models with larger storage capacity, camera problems on the 6 Plus model, as well as an initially undocumented "error 53" that appeared under certain circumstances.

[63][64] Apple responded to the bending allegations, stating they had only received nine complaints of bent devices and that the damage occurring due to regular use is "extremely rare."

[68] Twitter users claimed the seam between the glass screen and aluminum back of the iPhone 6 was to blame, with hair becoming caught within it.

Business Korea reported the issues were connected to the triple-level cell NAND storage of the affected models.

It was reported Apple had planned to switch the affected model lines back to multi-level cell flash, and address the performance issues on existing devices in a future iOS update.

[77][78] On February 18, 2016, Apple released an iOS 9.2.1 patch through iTunes which addresses this issue and admitted error 53 was actually related to a diagnostic check for inspecting the Touch ID hardware before an iPhone is shipped from its factories.

[79] Touchscreen control components on iPhone 6 logic boards have insufficient support, including a lack of underfill—which strengthens and stabilizes integrated circuits, and a lack of rigid metal shielding on the logic board unlike previous iPhone models; the touchscreen controller is instead shielded by a flexible "sticker".

[80][81] iFixit reported this issue, nicknamed "touch disease",[80][82][83] was a byproduct of the previous "Bendgate" design flaw because of the device's demonstrated lack of rigidity.

[83][84][85] The devices' successor, the iPhone 6s, is not afflicted by this flaw due to changes to their internal design, which included the strengthening of "key points" in the rear casing, and the re-location of the touchscreen controllers to the display assembly from the logic board.

[86] On August 30, 2016, a group of three iPhone 6 owners sued Apple Inc. in the United States District Court for the Northern District of California and filed for a proposed class action lawsuit, alleging Apple was engaging in unfair business practices by having "long been aware" of the defective design, yet refusing to acknowledge or repair it.

[82][87][88] On November 17, 2016, Apple officially acknowledged the issue and announced a paid repair program for affected iPhone 6 Plus models, stating; "some iPhone 6 Plus devices may exhibit display flickering or Multi-Touch issues after being dropped multiple times on a hard surface and then incurring further stress on the device".

The iPhone 6S & 6S Plus were introduced in September 2015 selling 13 million units which set the record for sales in the first three days from last years release.