It was written by Lovato along with Oak Felder, Alex Niceforo, Keith Sorrells, Laura Veltz, and Sean Douglas.

"29" received positive reviews from music critics, many of whom praised its lyrics and Lovato's vocals, and named it the best track on Holy Fvck.

Lovato performed "29" on The Tonight Show Starring Jimmy Fallon and included it on the set list of the Holy Fvck Tour (2022).

[1] On June 6, 2022, Lovato announced her eighth studio album, Holy Fvck, set to release on August 19, along with its cover artwork.

[6] Upon posting a snippet of the song on TikTok, fans speculated that the lyrics are a reference to Lovato's ex-boyfriend Wilmer Valderrama, whom she dated for 6 years.

[7] It quickly became a viral trend on the app, prompting people to share their stories about grooming and abusive relationships with an inappropriate age gap.

[13] AllMusic critic Neil Yeung claimed the most attention-grabbing moment on the album comes with "29", and described it as "a scathing takedown of a past relationship with mind-blowing lyrics".

She named "29" as "undeniably the stand-out track in every way", praised Lovato's powerful vocals and soaring drums and guitars, and said that "are goose-bump inducing, a bruising ache of emotion".

Ahlgrim praised the way that Lovato "manages to sing from a place of wisdom and maturity without shying away from the details", and the inclusion of "frank references to menstruation and daddy issues".

[17] Billboard journalist Stephen Daw ranked it as one of the best songs on the album, stating that "sounds like the kind of musing that comes after years of finding the right words to say about a traumatic event".

[24] Additionally, "29" peaked at number 14 on the component New Zealand Hot Singles chart published by Recorded Music NZ.