The song debuted on September 3, 2015 on Apple Music's Beats 1 radio station and was made available for digital download on the same day Jackson officially announced the studio album's release date and track list.
[3] Jackson announced she had founded her own label, Rhythm Nation, becoming the first female African-American recording artist to do so, while also planning the album to be distributed by BMG, as well as preparing herself for a new world tour in the same year.
[7] On the same day, the song was released to digital download and streaming for those who pre-ordered the album, as well as it premiered on Apple Music's Beats 1 radio station, hosted by Ebro Darden.
It is a mid-tempo R&B song, with its instrumentation consisting in a thumping bass and a subdued "funky" beat,[11][12] having a "distinctive Janet sound", according to some critics,[12] and a soul-sample,[13][14] while Jackson's vocals were considered "breezy" and "soulful".
Andy Kellman of AllMusic praised the "relaxed and wistful groove", as well as "her lead and background vocals in the chorus arranged to stellar effect", picking the song as one of the album's standout tracks.
"[21] Evan Sawdey of PopMatters called it "a solid mid-tempo groove, something that is all well and good until those multi-layered vocal harmonies come in during the chorus and we’re instantly transplanted back to Janet of old, her familiar coo still sounding remarkably fresh after all this time.
"[22] Maura Johnston of Time noted that its "space-age synth [...] blossoms into a sunny-day soul strut," while giving praise towards Jackson's voice, which according to her, "always notable for the emotion it could pack into even the simplest verse, [being] particularly suited to this type of laid-back R&B.
"[23] Mark Sundstrom wrote for Fuse that he was "obsessed" with the track and "sold" on the album, also praising its "rich harmonies" that "totally suits Janet's sexy, sultry vocals.
"[16] Anupa Mistry of Pitchfork called it a "giddy, grateful grown-woman song",[24] Citing "Unbreakable" as one of the album's "affecting surprises", USA Today writer Elysa Gardner named it "brightly infectious",[25] while Carolyn Menyes of Music Times perceived that it "retains the coolness of the first Unbreakable track fans have heard, 'No Sleeep,' while being totally thematically different, focusing on Jackson's return to the world of music.
"[27] While noting that "'Unbreakable' is also the title of a song that began her brother Michael’s final album before he died in 2009", Rob Tannenbaum of Billboard remarked that "the high chorus even sounds like something he might’ve written.