[7] The Galaxy S II has a 1.2 GHz dual-core "Exynos" system on a chip (SoC) processor,[8] 1 GB of RAM, a 10.8 cm (4.3 in) WVGA Super AMOLED Plus screen display and an 8-megapixel camera with flash and 1080p full high definition video recording.

[12][13] The Galaxy S II was popular and a huge success both critically and commercially,[14][15] selling 3 million units within its first 55 days on the market.

[2][25] On 13 March 2012, Samsung began to roll out upgrades to Android 4.0.3 "Ice Cream Sandwich"[26] through their phone management software KIES to users in South Korea, Hungary, Poland and Sweden.

[30] The Android 4.1 update backports the TouchWiz Nature interface and other features from the Galaxy S III, such as Direct Call, Pop-up Play, Smart Stay, and Easy Mode.

Additional applications include Kies 2.0, Kies Air,[32] AllShare (for DLNA), Voice Recognition, Google Voice Translation,[33] Google Maps with Latitude, Places, Navigation (beta) and Lost Phone Management, Adobe Flash 10.2, QuickOffice application and 'QuickType' by SWYPE.

For audio it supports FLAC, WAV, Vorbis, MP3, AAC, AAC+, eAAC+, WMA, AMR-NB, AMR-WB, MID, AC3, XMF.

[39] The Galaxy S II has a 1.2 GHz dual core ARM Cortex-A9 processor that uses Samsung's own 'Exynos 4210' System on a chip (SoC) that was previously code-named "Orion".

[40][41] This graphics GPU, supplied by ARM, is a move away from the PowerVR GPU of the Samsung Galaxy S.[42] The Exynos 4210 supports ARM's SIMD engine (also known as Media Processing Engine, or 'NEON' instructions), and may give a significant performance advantage in critical performance situations such as accelerated decoding for many multimedia codecs and formats (e.g., On2's VP6/7/8 or Real formats).

At the 2011 Game Developers Conference ARM's representatives demonstrated 60 Hz framerate playback in stereoscopic 3D running on the same Mali-400 MP and Exynos SoC.

[46] A newer Samsung Galaxy S II variant (i9100G) uses a 1.2 GHz dual core TI OMAP 4430 processor with PowerVR SGX540 graphics.

[48] The Samsung Galaxy S II uses a 108.5-millimetre (4.27 in)[11] WVGA (800 x 480) Super AMOLED Plus capacitive touchscreen that is covered by Gorilla Glass with an oleophobic fingerprint-resistant coating.

[52] User feedback on Internet forums as well as an in-depth review at Clove,[51] have expressed the Yamaha chip's inferior sound quality compared to that of the Wolfson chip featured in the original Galaxy S. On the back of the device is an 8-megapixel Back-illuminated sensor[53] camera with single-LED flash that can record videos in full high-definition 1080p at 30 frames per second.

[57] For the Galaxy S II, the industry standard micro USB port found on the bottom of the device can be used with an MHL connector for a TV out connection to an external display, such as a high definition television.

Additional accessories available include: The Samsung Galaxy S II GT-I9100G was released in late 2011, and is usually sold instead of the original GT-I9100 in certain markets (mostly Asia and some parts of Europe).

This difference in the SoC makes this variant incompatible with custom ROMs intended for the I9100, but it has been steadily gaining its own aftermarket support (such as from CyanogenMod[65]) due to the relative ease of development and the openness of the TI OMAP platform.

In Australia the Galaxy S II 4G (Model GT-I9210T) uses a Qualcomm processor and supports Telstra's and Optus' 4G networks.

[66] The Rogers Galaxy S II LTE (Model SGH-I727R) is identical to the AT&T Skyrocket, and features a larger screen 4.52", a bigger battery 1,850 mAh, and a different 1.5 GHz Qualcomm processor.

[67] Note that the Galaxy S II LTE has a different model number: I9210 and came out later and only in select markets, including Canada and South Korea.

Telus Mobility's 4G Galaxy S II X (Model SGH-T989D) is identical hardware-wise to the T-Mobile SGH-T989, including the Qualcomm 1.5 GHz dual core processor, larger 4.52 inch screen and 1,850 mAh battery.

[68] Although utilizing a different modem firmware, most custom ROMs running on T-Mobile versions can be flashed to the Telus T989D.

The ISW11SC uses the Samsung Exynos 4210 dual-core 1.4 GHz main CPU and a Qualcomm QSC6085 Modem chipset running at 192 MHz.

This phone features NFC functionality which is technically compatible with FeliCa RFID (such as with PASMO and SUICA payment systems) however, the software doesn't support the Japanese "Osaifu Keitai" mobile wallet and thus the phone cannot be used to make transactions with NFC in Japan.

[70] AT&T Mobility introduced a second variant of the device called the Galaxy S II Skyrocket (Model SGH-I727) on 6 November 2011.

The Captivate Glide differs from the other two AT&T Mobility variants primarily by the inclusion of a slide-out, physical QWERTY keyboard.

[74] The Sprint variant features four touch-capacitive buttons as opposed to the three-button hardware/capacitive combination found on the international version.

[75] The Galaxy S II is a touchscreen-only device, unlike the Epic 4G, which includes a physical QWERTY keyboard.

The phone has a Broadcom BCM28155 SoC with a 1.2 GHz dual-core processor and a VideoCore IV HW GPU instead of the Mali 400MP in the original Galaxy S II.

It uses a hyperglazed plastic body (the same as the Samsung Galaxy S III) and is available in Chic White and Dark Blue.

"[83] CNET UK gave the device a favorable review of 4.5/5 and described it as "one of the slimmest, lightest mobiles we've ever had the privilege to hold.

"[88] After slightly over one month since its debut, more than 1 million units of Samsung Galaxy S II were activated in South Korea.