It is distinguished from its predecessor through a internal battery with an increased charging speed but a decreased capacity, an optically stabilized camera, sound in slow motion video recordings, a glass back, and it lacks a user-replaceable battery, a memory card slot, water resistance, and MHL-to-HDMI connection for viewing on an external monitor or television set.

The S6 and S6 Edge were unveiled on March 1, 2015, during the Samsung Unpacked press event at MWC Barcelona, and released April 10, 2015, marking a counter-utilitarian and fashion-oriented course in the Galaxy S series.

Although the overall design of the Galaxy S6 still features characteristics from prior models, its construction was revamped to use a metal unibody frame and glass backing instead of plastic.

The Galaxy S6 received mostly positive reviews from critics, who praised the devices' upgraded build quality over prior models, along with improvements to their displays, performance, camera, and other changes.

However, Samsung's decision to remove the ability for users to expand their storage using microSD cards or remove the battery, and the lack of water resistance were panned as being potentially alienating to power users, and the S6 Edge was also panned for not making enough use of its curved display to justify its increased cost over the standard model on-launch.

[4] The S6's design was officially teased in a promotional webpage released by T-Mobile US on 22 February 2015, which showed a curved body and carried the tagline "Six Appeal".

As part of these goals, a number of features and capabilities seen on the Galaxy S5 were removed, such as its waterproofing USB 3.0 port, MicroSD expandable internal storage and Mobile High-Definition Link (MHL).

[11] The decision of denying users the replacement of their batteries is claimed to have been postponed throughout the Samsung Galaxy S series until users be "confident about charging their phones", as stated by Justin Denison, then-vice president of product strategy at Samsung, on stage at the Unpacked 2015 Episode 1 keynote event,[12][13] whereas a mockery commercial for the preceding Galaxy S5 against iPhones' non-replaceable batteries was aired the previous year, referring to its users as "wall huggers", citing their incessant dependence on wall charging.

[17] The Galaxy S6 line retains similarities in design to previous models, but now uses a unibody frame made of aluminium alloy 6013[18] with a glass backing, a curved bezel with chamfered sides to improve grip, and the speaker grille, as well as the 3.5mm headphone connector was moved to the bottom next to the MicroUSB 2.0 type B charging port, located there for the first time in the Samsung Galaxy S series.

[10][15][16][19] The Galaxy S6 was also available in a limited Iron Man edition, in promotion of Avengers: Age of Ultron, with six additional colour options.

The processor is Samsung's first to use a 14 nm FinFET manufacturing process, which the company stated would improve its energy efficiency.

For its rear-facing camera, Galaxy S6 uses the same image sensor (Sony Exmor RS IMX240/Samsung ISOCELL S5K2P2) with optical image stabilization as the Galaxy Note 4,[25] For the first time in a Samsung flagship device, a bundled slow-motion video editor allows viewing custom parts of the recorded footage at adjustable speeds and exporting it for sharing.

[25] The setting menu is no longer a four-column icon+label grid floating on top of the camera viewfinder, but a list on a separate page.

If enabled in the settings, it is accessible with three home button presses rather than a previously used swipe gesture, and shrinks the screen's view port size to facilitate single-handed usage.

It enables new features such as "Google Now on Tap", which allows users to perform searches within the context of information currently being displayed on-screen, and "Doze", which optimizes battery usage when the device is not being physically handled.

[43][44] The Galaxy S6 is the first Samsung flagship device to offer a torch toggle shortcut in the drop-down quick control menu instead of a home screen widget, making it accessible quicker and without having to leave an opened app.

[10][30][32] The Verge concluded that the S6 and S6 Edge were "the first time I've felt like Samsung might finally be grappling with the idea of what a smartphone ought to be on an ontological level.

As such, Samsung was criticized for providing no true justification for purchasing the S6 Edge over the non-curved S6, explaining that "it doesn't do anything beyond the base model, but it'll be worth the money to some people because of how it looks and the air of exclusivity it communicates.

Still, facing competition by other vendors that have led to declining market share, a lower net profit, and foreseeing a "difficult business environment" for the second half of the year, Samsung announced during its second quarter earnings report in July 2015 that it would be "adjusting" the price of the S6 and S6 Edge.