The group rose to fame in 2009 with the single "Gee", which claimed the top spot on KBS's Music Bank for a record-breaking nine consecutive weeks and was Melon's most popular song of the 2000s decade.

The group's fourth Korean studio album, I Got a Boy (2013), was supported by the title track, which won Video of the Year at the inaugural YouTube Music Awards.

The group's signature musical styles are characterized as electropop and bubblegum pop, though their sound has varied widely, incorporating various genres including hip hop, R&B, and EDM.

[7][8] The first member of the group to join SM Entertainment's training system was Jessica in 2000, after she and her sister, Krystal Jung, were scouted in a mall in South Korea during a family vacation.

[56][57] Amidst their Japanese activities, they also participated in the SMTown Live '10 World Tour alongside their labelmates, which started on August 21 at Seoul Jamsil Olympic Stadium.

[70] Within its first month of release, Girls' Generation sold 500,000 copies and earned a double platinum certification by the Recording Industry Association of Japan.

[79] To help The Boys connect with audiences worldwide, the group made their debut on US television upon performing on Late Show with David Letterman on January 31 and Live!

[84][85] The group's endeavor to the United States, meanwhile, was met with limited success;[86] The Boys entered the Billboard Top Heatseekers at number 17 and sold 21,000 copies.

[92] In December 2012, Girls' Generation released "Dancing Queen"—a remake of British singer Duffy's "Mercy" (2008)—as the lead single from their then-upcoming 2013 Korean studio album.

[93] On New Year's Day of 2013, the group released their fourth Korean studio album titled I Got a Boy,[94] and held an MBC special television program, Girls' Generation's Romantic Fantasy.

[97] The title track reached number one on Billboard's Korea K-Pop Hot 100 and the Gaon Digital Chart,[98] and sold over 1.35 million copies.

SM Entertainment confirmed her departure, stating Jessica was no longer a member of Girls' Generation due to conflicts between her and the group's schedules.

[152][153][154] Girls' Generation reunited in September 2021 with an appearance on variety show You Quiz on the Block, which marked their first group activity in four years.

[159][160] The group performed at the SM Town Live 2022 concert during the same month,[161] and also held a sold-out special event "Long Lasting Love" in September 2022.

[163] In April 2012, SM Entertainment formed a subgroup of Girls' Generation named TTS (or TaeTiSeo), composed of three members: Taeyeon, Tiffany, and Seohyun.

The range of activities include roles in movies, dramas and plays, variety shows appearances, starting personal YouTube channels, and also continuing to release music individually.

Girls' Generation's key advantage as a group is performance and vocal line so we worry a lot over songs that will fulfill both of these areas."

[199] Their 2011 single "The Boys" departs for a more "mature" style from the group's previous emphasis on "cutesy" themes;[197] it incorporates elements from hip hop, a genre that Girls' Generation had never ventured into.

[200] The titular studio album, according to AllMusic's reviewer Tim Sendra, includes uptempo dance tracks "with a straight pop radio feel.

"[201] Girls' Generation's 2012 single "Dancing Queen"—a remake of British singer Duffy's "Mercy" (2008)—features a "funky pop" production, as opposed to the group's signature electropop sound.

[93] Their 2013 single "I Got a Boy" was noted for its eclectic musical style, utilizing various genres ranging from bubblegum pop, electropop and drum and bass to pop-rap, EDM, and dubstep.

[194] Both aforementioned singles' parent album, I Got a Boy (2013), combines elements from a wide range of genres such as 1980s new wave, EDM, and classic and contemporary R&B.

[205] AllMusic's Heather Phares also noted inspirations of EDM, hip hop, traditional K-pop sound, and late-1980s europop on the EP, which she labelled "a set of songs that offers something for every kind of Girls' Generation and expands their musical reach.

"[206] The group's 2015 album Lion Heart brings back their signature bubblegum pop sound;[207] its third single "You Think", however, is a hip hop song that incorporates trap beats in its instrumentation.

[72] The group's 2011 single "The Boys" was noted for conveying a feminist theme and was compared to Beyoncé's 2011 single "Run the World (Girls)" for the same "women-powered" content;[216] Eun-Young Jun in the book The Korean Wave: Korean Media Go Global (2013) noted its lyrics for depicting "sexually daring women" who are confident in their sexuality.

[217] In 2009, the group set the "colorful skinny jeans" fashion trend with "Gee",[218][219] and later opted for a marine-inspired image on wearing uniforms and shorts that highlighted their legs with "Tell Me Your Wish (Genie)".

"[214] Eun-Young Jung in the book The Korean Wave opined that the group's concepts fall into two main categories—"innocent, cutesy, happy" (early singles "Gee", "Genie", "Oh!")

[240] Japanese magazine Nikkei Business suggested the group's international expansion and success was the musical equivalent to Samsung's global trend.

[257] Billboard placed "I Got a Boy" at number 21 on their list of the 100 Greatest Girl Group Songs, describing it as "proof to why girl-group music is in a league of its own in terms of excitement and boundary pushing".

[294] Writing for The Korea Herald, Choi Ji-won highlighted the significance of their return in "an industry where most girl groups cannot stand the test of time", especially considering that they are in different companies.