Coldplay's musical style has generally been regarded as alternative rock, pop rock, post-Britpop, and pop. Chris Martin once proclaimed the band's music as "limestone rock" in comparison to "hard rock". The band's music has been called "meditative" and "blue romantic"; it "[reflects] on their emotions" and Martin "endlessly examine[s] his feelings". Coldplay started out as one of many earnest post-Britpop bands. In the late 1990s, the EPs released by the band had characteristics of dream pop, setting them apart from later studio albums. The tone of the band's first studio album Parachutes, which saw them emerge as one of the most prominent modern bands in British popular culture, was described as melodic pop with "distorted guitar riffs and swishing percussion" but also being "exquisitely dark and artistically abrasive". Such alternative rock style has been compared to bands like U2, Oasis, Radiohead and Travis. The band acknowledges the Scottish alternative rock band, Travis, as a major influence on their earlier material.

Chris Martin and Jonny Buckland first met during their orientation week at University College London (UCL) in September 1996. The pair spent the rest of the university year planning a band, ultimately forming a group called Pectoralz. Guy Berryman, a classmate of Martin and Buckland, later joined the group. By 1997, the group, who had renamed themselves Starfish, performed gigs for local Camden promoters at small clubs. Martin also had recruited his longtime school friend Phil Harvey, who was studying classics at the University of Oxford, to be the band's manager. Coldplay have since accepted Harvey as the fifth member of the group. The band's line-up was completed when Will Champion joined to take up percussion duties. Champion had grown up playing piano, guitar, bass, and tin whistle; he quickly learned the drums (despite having no previous experience). The band finally settled on the name "Coldplay" which was suggested by Tim Crompton, a local student who had been using the name for his group.

By 1997, Martin had met Classics student Tim Rice-Oxley. During a weekend in the English village Virginia Water in Surrey they asked each other to play their own songs on the piano. Martin, finding Rice-Oxley to be talented, asked him to be Coldplay's keyboard player but Rice-Oxley refused as his own band, Keane, was already active. Days after, this event would shape the second line-up of Keane and keep Coldplay's unaltered, thus leaving both bands as quartets. In 1998, the band released 500 copies of the Safety EP. Most of the discs were given to record companies and friends; only 50 copies remained for sale to the public. In December of that year, Coldplay signed to the independent label Fierce Panda. Their first release was the three-track Brothers and Sisters EP, which they had quickly recorded over four days in February 1999.

The band initially planned to record their debut album in the space of two weeks. However, tours and other live performances caused the recording to spread out between September 1999 and April–May 2000. The album was recorded at Rockfield Studios, Matrix Studios, and Wessex Sound Studios with Producer Ken Nelson, although the majority of Parachutes' tracks were recorded at Liverpool's Parr Street Studios (where they accessed three studio rooms). The mixing process on all songs for the album was done by American Engineer Michael Brauer in New York. During that period, they played on the Carling Tour, which showcased up-and-coming acts.

Parachutes was nominated for the Mercury Music Prize in September 2000. Having found success in Europe, the band set their sights on North America, by releasing the album there in November 2000, and started the US Club Tour in February 2001. At the 2001 Brit Awards in February, Coldplay earned awards for Best British Group, and Best British Album. Although Parachutes was a slow-burning success in the United States, it eventually reached double-platinum status. The album was critically well received and earned a Best Alternative Music Album honours at the 2002 Grammy Awards. Chris Martin claimed, after the release of Parachutes, that the album's success was intended to elevate the band's status to the "biggest, best band in the world." After single-handedly managing the band until early 2001, Phil Harvey resigned from his role due to the stress of performing a role usually requiring a team of people. Harvey then took on the role of "creative director" and is often referred as the official fifth member by the band, while Dave Holmes took over as the band's manager.

After the success of Parachutes, Coldplay returned to the studio in September 2001 to begin work on their second album, A Rush of Blood to the Head, once again with Ken Nelson producing. Since the band had never stayed in London before, they had trouble focusing. They decided to relocate in Liverpool, where they recorded some of the songs on Parachutes. Once there, vocalist Chris Martin said that they became obsessed with recording. "In My Place" was the first song recorded for the album. The band released it as the album's lead single because it was the track that made them want to record a second album, following a "strange period of not really knowing what we were doing" three months after the success of Parachutes. According to Martin "one thing kept us going: recording 'In My Place'. Then other songs started coming."

The band wrote more than 20 songs for the album. Some of their new material, including "In My Place" and "Animals", was played live while the band was still touring Parachutes. The album's title was revealed through a post on the band's official website. The album was released in August 2002 and spawned several popular singles, including "In My Place", "Clocks", and the ballad "The Scientist". The latter was inspired by George Harrison's "All Things Must Pass", which was released in 1970.

During the early years, Coldplay became widely known in the media for giving 10 per cent of the band's profits to charity, which they continue to do. Bassist Guy Berryman said, "You can make people aware of issues. It isn't very much effort for us at all, but if it can help people, then we want to do it." The band also asks that any gifts intended for them are donated to charity, according to a response on the FAQ section of Coldplay's website. Martin spoke out against the 2003 invasion of Iraq by the US, UK and other forces during the Teenage Cancer Trust show at London's Royal Albert Hall on 24 March 2003, where he encouraged the sell-out crowd to "sing against war". He would later endorse the US Democratic presidential candidates John Kerry and Barack Obama in 2008 and 2012 respectively.

From June 2005 to March 2007, Coldplay went on their Twisted Logic Tour, which included festival dates like Coachella, Isle of Wight Festival, Glastonbury and the Austin City Limits Music Festival. In July 2005, the band appeared at Live 8 in Hyde Park, where they played a rendition of The Verve's "Bitter Sweet Symphony" with Richard Ashcroft on vocals. On 28 August, Coldplay performed "Speed of Sound" at the 2005 MTV Video Music Awards in Miami. In September, Coldplay recorded a new version of "How You See the World" with reworked lyrics for War Child's Help!: A Day in the Life charity album. In February 2006, Coldplay earned Best Album and Best Single honours at the Brit Awards. Two more singles were released during 2006, "The Hardest Part" and "What If".

In October 2006, Coldplay began work on their fourth studio album, Viva la Vida or Death and All His Friends, with Producer Brian Eno. Taking a break from recording, the band toured Latin America in early 2007, finishing the Twisted Logic Tour by performing in Chile, Argentina, Brazil, and Mexico. After recording in churches and other venues in Latin America and Spain during their tour, the band said the album would likely reflect Hispanic influence. The group spent the rest of the year recording most of the album with Eno.

Upon release, Viva la Vida or Death and All His Friends topped the album charts worldwide, and was the world's best-selling album of 2008. It hit number one on the UK album chart, despite having come on the market only three days previously. In that time, it sold 302,000 copies; the BBC called it "one of the fastest-selling records in UK history". By the end of June, it had set a new record for most-downloaded album ever. In October 2008, Coldplay won two Q Awards for Best Album for Viva la Vida or Death and All His Friends and Best Act in the World Today. On 9 November, Coldplay were named the World's Best Selling Act of 2008 at the World Music Awards in Monte Carlo. They also picked up two other awards, World's Best Selling Rock Act and Great Britain's Best Selling Act. The band followed up Viva la Vida or Death and All His Friends with the Prospekt's March EP, which was released on 21 November 2008. The EP features tracks from the Viva la Vida or Death and All His Friends sessions and, as well as being available on its own, was issued as a bonus disc with later editions of Viva la Vida or Death and All His Friends. "Life in Technicolor II" was the only single released from the EP.

Coldplay have won numerous music awards throughout their history, including the American Music Award, nine Brit Awards (including winning the Best British Group four times), five MTV Video Music Awards, seven MTV Europe Music Awards, three World Music Awards, six Billboard Music Awards, and seven Grammy Awards out of 32 nominations. 2009 was their most successful year having received seven Grammy Award nominations at the 51st Grammy Awards, and won three. Coldplay have sold over 100 million records worldwide.

Despite their worldwide popularity, the band has remained protective of how their music is used in the media, refusing its use for product endorsements. In the past, Coldplay turned down multi-million dollar contracts from Gatorade, Diet Coke, and Gap, who wanted to use the songs "Yellow", "Trouble", and "Don't Panic" respectively. According to frontman, Chris Martin, "We wouldn't be able to live with ourselves if we sold the songs' meanings like that." The song "Viva la Vida" was featured in a commercial for the iTunes Store, advertising its exclusive availability of the single as a digital download on iTunes. Additionally, Chris Martin appeared at an Apple Inc. Special Event on 1 September 2010, playing a number of songs, and also thanked Apple for their assistance in marketing "Viva la Vida". After the death of Steve Jobs, Coldplay performed four songs at Apple's Campus in Cupertino, further thanking Jobs for the support he gave them.

In 2011, Coldplay endorsed the song "Freedom for Palestine" by posting a link to the video. In less than a day 12,000 comments were posted to it. Some threatened to boycott the band, and a Facebook group was created that demanded an apology to Israel. The link to the song was eventually removed from their Facebook wall. According to Frank Barat of OneWorld, the link was not removed by Coldplay but by Facebook after "thousands of people (and computer generated posts) reported it as abusive."

Coldplay supports Amnesty International and performed for them at The Secret Policeman's Ball fundraiser in 2012. Martin is regarded as one of the most visible Celebrity advocates for fair trade, supporting Oxfam's ongoing Make Trade Fair campaign. He has been on trips with Oxfam to assess conditions, has appeared in its advertising campaign, and is known for wearing a "Make Trade Fair" wristband during public appearances (including at Coldplay concerts). The band were also filmed for Make Poverty History, clicking their fingers.

On 9 August 2013, Coldplay announced the release of their song, "Atlas", which featured on the Soundtrack for the film The Hunger Games: Catching Fire. Its release got pushed back to 6 September 2013 (everywhere but the UK) and 8 September (UK). In December 2013 it was announced that Future Coldplay releases will be distributed by Atlantic Records in the US due to restructuring within Warner Music Group following the purchase of Parlophone Records from EMI.

Album Artists (www.albumartists.co.uk) staged an exhibition of art from Mylo Xyloto at Proud Gallery in Camden to support the charity Kids Company in November—December 2012. The exhibition raised over £610,000 for the children's charity which supports disadvantaged children in London. In November 2014, Martin joined the charity group Band Aid 30, performing alongside current British and Irish pop acts on the latest version of the track "Do They Know It's Christmas?" to raise money for the 2014 Ebola crisis in Western Africa—this was the second time Martin has contributed to a Band Aid recording having performed in the 2004 version (Band Aid 20).

On 27 November 2015, the first dates to their 2016 A Head Full of Dreams Tour were announced. Latin American and European legs were listed, which included three dates at Wembley Stadium, London in June. The North America Tour, an extra Wembley concert, and an Oceania tour, were later added. On 5 December, the band headlined the opening day of the 2015 Jingle Bell Ball at London's O2 Arena. On 7 February 2016 they headlined the Super Bowl 50 halftime show. The band were joined by Beyoncé and Bruno Mars. In April 2016, the band were named the sixth best selling Artist worldwide in 2015.

In June 2016 the band supported Vote Remain in the United Kingdom European Union membership referendum. Following the Brexit result which saw 52% of the UK voting to leave the EU (despite the majority of younger people voting remain), Chris Martin stated: "This decision does not represent us or indeed most of our generation and the generation following us."

On 4 June 2017, Coldplay performed at the One Love Manchester benefit concert for the victims of the 2017 Manchester Arena bombing where they also performed with Liam Gallagher on "Live Forever". On 24 September 2017, Chris Martin and Jonny Buckland performed as special guests at the "Concert for Charlottesville", a unity concert in Charlottesville, Virginia after the events of the "Unite the Right rally" that occurred on 12 August 2017.

Coldplay is contributed to Plastic Oceans Album by Artists' Project Earth (APE) which was released on 20 February 2018 at the Ocean Plastics Crisis Summit in London. The motive of the album is to raise awareness and funds aiming to counter plastic pollution of the ocean.

Speaking to Australian radio station 2Day FM, Chris Martin revealed that the title for their next album: "is much easier to pronounce." Martin debunked speculation that they were taking a break from touring by saying, "This three-year break idea only came about because I said at a gig in Australia that we might not be back there for three years. That’s probably true, but that’s just how a world tour works. No chance are we taking a three-year break.”