Demi received generally favorable reviews from music critics, who complimented Lovato's vocal performance. The album debuted number three on the US Billboard 200 with the first-week sales of 110,000 copies, becoming her best-selling debut week of her career. The album proved similarly successful on international markets, reaching the top five in countries including Canada, Ireland, Italy, Mexico and Spain. It also reached the top three in the Brazil. It reached the top 40 in Australia, Austria, Croatia, Germany, Greece, New Zealand, Norway, Portugal, Sweden, Switzerland and the UK. The album was certified triple platinum in Brazil and Gold in Colombia, Canada and Mexico, becoming her biggest selling international album to date.
The lead single, "Heart Attack" peaked at number 10 on the Billboard Hot 100, becoming her third highest-charting single in the country thus far. It has since been certified 2× Platinum in the US, becoming her fastest selling single to date. The second single "Made in the USA" was released on July 16, 2013. It peaked at number 80 on the Hot 100. The third single "Neon Lights" was released on November 19, 2013, peaked within the top 40 of the Hot 100 and reached number 7 on the BillboardMainstream Top 40. Its fourth single "Really Don't Care" was released on May 20, 2014.
In April 2012, Lovato began writing the songs from her fourth studio album, after the commercial success of her third studio album Unbroken (2011). At the same time, the album was recorded during Lovato's appearance as a mentor on the second season of The X Factor (U.S.). Lovato chose the title of the album Demi, because it was her first album intended for a more mainstream audience and wanted for those who did not know who she was. Lovato also explained a "sequel" of the song "Skyscraper" (2011) is included. After the album was released, it was revealed that "Warrior" was intended to be a sequel of "Skyscraper". She stated "I'm incredibly proud of this album" and "It's better than anything I have ever done! I experimented with a variety of different sounds and poured my heart into writing these songs. I'm so excited for everyone to finally get the chance to hear them!". On May 6, 2013, Lovato asked her Twitter followers to "unlock" the entire album by putting song titles in hashtags. A special website lovaticsspeeduptime.com was launched, displaying all the songs next to a clock that would turn as tweets would be sent. Once a song became a trending topic, its YouTube video was made available on VEVO. All the songs were unlocked within four hours. An iBooks-exclusive e-book titled Demi (The Book) was released on June 11, 2013. The book gives fans behind-the-scenes access to the singer, including never-before-seen footage and interviews. In one clip, she says that being honest and open is not only the message she's sending her fans in the book but also on her album release. She said, "This album I've had enough time to really reflect on personal experiences and look back at my life after having overcome a bunch of things. I've been more aware of myself; therefore, when you listen to the album, you can really tell in the lyrics and in the emotion and everything I worked really, really hard on this album, and hopefully you'll be able to hear that.
"I always want to make positive music. Obviously I'm gonna have my songs about heartbreak and break-ups, but with this album… I get sick of listening to the radio and hearing only music that's talking about partying and drinking and getting high. That's not what I do. It's not what I stand for."
—Lovato on the lyricism she wanted to convey with Demi.
Lovato herself described Demi as "good old American pop music", which was deeply influenced by her breakout single "Give Your Heart a Break" and she felt the "super catchy" lyrics as well as the beat of the song resonated with fans, which she wanted to further explore on the album. According to Lovato, her previous album Unbroken contained songs that she got sick of "a lot faster", so she wanted to "have songs that excited" her on Demi. Musical genres on the album range from pop rock to synthpop and bubblegum pop. Apart from "catchy songs" such as the mid-tempo track "Without the Love", "emotional songs" are also included on Demi. This is demonstrated on "Shouldn't Come Back" and "Warrior"; which Lovato states are too personal to perform live, comparing them to a song from Unbroken entitled "For the Love of a Daughter".Billboard states that "Warrior" has Lovato declaring herself "a phoenix that has risen from all-too-public ashes", with emotional lyrics such as: "I've got shame, I've got scars, that I will never show/I'm a survivor, in more ways than you'll know". Speaking of "Warrior", the singer stated: "That song was probably the hardest and easiest song to write on the album. I was writing about personal experiences, and it's the type of song where you can't fit all of it into one song". The theme of Americanism on the album is evident on the track "Made in the USA", a patriotic love song inspired by "American love stories" in the 1930s. The song incorporates pop, rock, and country. Stripped down piano ballads on Demi includes, "In Case", which contains lyrics about heartbreak and "Nightingale". The upbeat songs "Really Don't Care" and "Something That We're Not" are produced to suit of Lovato's "overpowering pipes".
In June 2013, Lovato said her interview of the fourth album to thank for her fans who known her in the past and her recovery, stated: "My life has changed so much. I am vulnerable and honest in this record, the way I've always wanted to be. I was ready to come out of the darkness". The album referenced of the writing process as "therapeutic", Lovato said: "It helped me get rid of my demons, I am a warrior now. I've been through so much in the past years, it was hard to find the courage to get out of it and write about it, I was afraid no one would understand my message. I spent so much time trying to figure out what the right thing to do was, that I got distracted along the way by fun and temptations ad that's why I ended up in rehab at 18".
The album received generally positive reviews from music critics. According to review aggregatorMetacritic, the album has a score of 64/100 based on 6 reviews. Jason Lipshutz from Billboard gave a positive review, saying that "the singer has a strong grip on her skills as a performer, but is still chiseling away at the formula that works best for her as an artist, and is unwittingly putting that self-discovery on display here." Jon Caramanica from The New York Times also gave a positive review, saying that it is "[an] often impressive fourth album."Stephen Thomas Erlewine from AllMusic gave a more mixed review, rating the album three stars out of five, saying that "Ultimately, this isn't an album of purpose, it's a collection of moments, and it has just enough good ones to solidify Demi Lovato's comeback." Jody Rosen from Rolling Stone awarded the album three stars out of five, saying that "It's predictable stuff—sassy songs, lovelorn songs, a couple of pop-psych pep talks—but Lovato is good company, and her voice has gustiness and character." Tamsyn Wilce from Alter The Press! gave the album four and a half stars out of five, praising "Neon Lights" as a highlight and concluding " it shows just how strong her vocal chords are and the variation of styles that she can completely work to make her own. If you’re not a fan of pop music, you'll absolutely hate it, but everyone has their little guilty pleasures – except we don't even feel the slightest bit guilty for listening to this album at full volume. Natalie Palmer from Entertainmentwise also have the album a positive review, stating "Pop rock is definitely Demi Lovato's genre and she owns it so well. When it comes to role models Demi should be seen as one of the best. Her lyrics speak truthfully about life, love and disaster and there's nothing too in depth. However whilst remaining matter of fact she is still able to materialise exactly what she is trying to convey."
Melissa Maerz from Entertainment Weekly, however, gave the album a mixed review and graded it C+, saying that "it's too bad that her new album Demi, sounds like such a decisive return to teen pop. Transformed from an edgier young woman back into America's sweetheart." Marc Hirsh from The Boston Globe was also mixed, saying that "Demi sounds like Lovato's grasping for hits, when she used to sound like she was making music and having fun." although many critics sighted the comment as "unnecessary" and praised Lovato's musical versatility. Melinda Newman from HitFix have the album a B-, commenting "The problem with "Demi" is that too much of the music here is so generic that it could be any teen queen delivering these tunes." However she went on to conclude "For those who are looking for a largely uptempo album that fits squarely into much of the pop landscape on radio today, Demi will be a pleasing fit."Alter The Press!, who had previously raved about the album upon its initial release, placed the album at number 8 on its list as one of the best albums of 2013.
The album debuted number three on the US Billboard 200 with first-week sales of 110,000 copies, behind Vampire Weekend's Modern Vampires of the City and George Strait's Love Is Everything, thus becoming the highest selling opening week of Lovato's career. In the United Kingdom, the album debuted at number ten on the UK Albums Chart, with sales of 10,658 copies sold in its first week. With the debut, it became her first album to breach the Top 40 in the country. The album has gone triple platinum in Brazil, and gold in three other nations as of January 2014. The album has sold 400,000 copies in the US as of July 2014 and 900,000 copies worldwide as of July 2014.
"Heart Attack" was released as the lead single from the album on February 24, 2013. The song was written by Mitch Allan, Jason Evigan, Sean Douglas, Nikki Williams, Aaron Phillips and Lovato and produced by The Suspex. The song debuted at number 12 on the Billboard Hot 100 chart with first week sales of 215,000 copies, becoming a sales record for Lovato at the time, and also being the third highest opening week for a single at the time. The song later broke into the upper-tier and peaked at number 10, becoming Lovato's third song to do so. The song also reached a peak at number 3 in the UK, her first single to crack the top ten in the country. The music video was filmed on March 13, 2013 and released on April 9, 2013. Lovato performed the song live on several shows, including The Ellen DeGeneres Show, Good Morning America and Jimmy Kimmel Live!, The song has since been certified 2× Platinum in the US as well as in Canada, as well as Silver in the UK and Gold in Australia, Denmark, New Zealand and Sweden.
"Made in the USA" was released as the album's second single on July 16, 2013. Lovato performed the song live at several concerts including Good Morning America's Summer Concert Series on June 28, 2013, as well as the 2013 Teen Choice Awards. The music video was released on July 17, 2013. While the song received positive reviews from critics, it failed to chart significantly, peaking at number 80 on the Billboard Hot 100. It managed to peak within the top 20 in Belgium, Lebanon and Portugal, as well at number 40 on the US Mainstream Top 40 and number 45 on the US Digital Songs charts.
"Neon Lights" was released as the album's third single on November 19, 2013. On September 29, 2013, Lovato announced the name of her concert tour, the Neon Lights Tour, and soon after that "Neon Lights" would become the third single from the album. The song, with its prominent EDM influences, covered new ground for Demi, who had been previously known for her pop ballad singles. The song received mixed reviews, with critics praising the song, but criticizing its placement on the album. Despite this the single began relatively well, with the accompanying music video being released on November 21, 2013. The song has since reached number 2 on the Ukraine Dance Charts. The song has done moderately well internationally, most significantly in New Zealand, where it has since peaked at number 12 and been certified Gold. It reached number 36 on the Hot 100, peaking at this position for three non-consecutive weeks. It also topped the US Hot Dance Club Songs chart at number one and became Lovato's third top 10 single at Mainstream Top 40, reaching number 7. It has since been certified Platinum in the US.
"Really Don't Care" featuring British recording artist Cher Lloyd, was released as the fourth single from the album on May 20, 2014. The week before it was officially serviced to US radio, it charted at number 10 at Mainstream Top 40, being her fourth top 10 single on the chart.