This is how you know you're hot: Numerous American critics put you on their 2006 year-end best-of lists even though your album doesn't come out until Jan. 30, 2007.

Which is what happened to 21-year-old British singer Lily Allen, whose "Alright, Still" arrived here six months after its release at home. Apparently, nobody wanted to miss this elevator while it was still on the ground floor. Blender magazine pre-canonized Allen as "The Number One Reason to Love '07," while GQ crowned her "the first lady of MySpace."

The latter is a big part of the story. Allen set up her own MySpace page in late 2005, while her label was still trying to figure out what to do with her. She posted demos of her own songs, fans responded and escalating viral buzz turned Allen into the "it" girl for social networking alterna-systems, evidenced by millions of downloads and her 135,000-and-counting MySpace cyber friends.

Allen is not the first Internet-fueled pop phenom, but such broadband-speed success stories are still rare. She's a streetwise songwriter, able to capture the vagaries of youthful romance and daily life in smartly observed reggae- and ska-infused pop songs that tend to be bright on the surface and dark at their center.

That's especially true of Allen's breakthrough single, "Smile," built on a sunny sample from the Soul Brothers' '60s classic "Free Soul" that masks the venom of lyrics evoking a cheated-on girl's joy at the misery she visits on her former boyfriend. The Sophie Muller-directed video documents Allen's revenge: She hires thugs to beat up her DJ-ex, then trash his apartment and scratch his vinyl records while she's consoling him in a coffee shop — where she puts laxative in his coffee!

(Allen's inspiration, DJ Lester Lloyd, may have gotten the last laugh: When the single hit No. 1, he sold the story of their romance to the British tabloids — sample headline, "We Were Off Our Heads on E ... The Sex Was Out of This World" — for about the same amount of money Allen got as an album advance.)

EXUDING GIRL POWER

"Smile" is not the only pistol in Allen's bandoleer. "Not Big" belittles an unnamed ex who can't deliver in bed. "Knock 'Em Out" serves up pithy ripostes against unwanted attention from clueless men. Even the album's one fairly traditional love song, "Littlest Things," is sung over the piano break from a theme to the soft-core "Emmanuelle" films.

The album is Girl Power 2.0, though Allen suggests it's at least partly a facade.

"I'm quite a self-conscious person and lack self-esteem in a lot of ways," Allen, who is headlining the inaugural MTV Discover and Download Live tour, explained recently from New York, "so my way of dealing with that is to be quite sharp and pretend to people that I'm really confident and can handle myself. I think that's deflected a lot of attention from the real me, and I think that really comes across in my music. But people that are music lovers can dissect that, and that's what they like about it."

As the British tabloids and music media have enjoyed trumpeting, Allen was a handful growing up in West London, one of three children of comedian-actor Keith Allen and Alison Owen, an Oscar-nominated film producer (for 1998's "Elizabeth"). Her parents separated when Lily was 4, and she grew up with, and still lives with, her mother. She attended more than a dozen schools, most quite exclusive and several of which she was expelled from.

In 2002, Allen had a record deal that fizzled, so she worked briefly as a florist before deciding it was easier to go to bed at 4 a.m. than to get up at that hour to go to work. She hooked up with production team Future Cut (Darren Lewis and Tunde Babalola), which had made a name for itself in drum-n-bass in the late '90s. The team did the beats, Allen the lyrics and melodies, building on the reggae/punk/ska/pop/calypso neighborhood sound she'd grown up with. Allen calls the album "an updated version of that to make it a little more relevant to our times."

Their first song: "Smile." Another early track, "LDN" (text-message shorthand for London), used a sunny calypso-tinged melody to underscore Allen's ambivalence about her home town. "Sun is in the sky/ oh, why, oh, why would I want to be anywhere else," she sings. "Everything seems nice/ But if you look twice/ You can see it's all lies." The video offers scenarios with Magritte-like dualities as shadows fall, as when a young man helping an old woman with her shopping bags ends up mugging her.

UNKNOWN TO 'NET STAR

In September 2005, Allen signed with Regal, which wanted her to work with more established writers and producers. Instead, Allen uploaded her songs on MySpace that November and assiduously blogged about fellow musicians and celebrities. Fans e-mailed tracks to others, with various online music media outlets linking up along the way. By last April, the previously unknown Allen had 40,000 cyber pals, a million downloads and the begrudging OK from her label to do it her way.

"It wasn't like the record company didn't like my music, or they would never have signed me in the first place," she says. "But I don't think they thought (the music) was there yet, and MySpace just gave them more confidence. ... MySpace was a bit of relief for all of us, 'cause I was happy with what I was doing, and I couldn't understand why everyone else didn't think it was there."

With the album slated for release in England in July, Allen played her first live date in May at a small London club. "We had an ad on MySpace, and 1,000 people showed up at a 200-seat club — it was definitely quite a special way of doing it," she says. "And people knew all the lyrics before that!"

Allen isn't rail thin, like her British peer Amy Winehouse, and she enjoys her left-field "look," a meld of '60s hairdo, neon eye shadow, oversized costume jewelry, and colorful cocktail dresses atop Nike sneakers.

"I've always been a fashion icon in my head," Allen laughs before adding, more seriously: "I feel happy, and I feel proud of myself, that I haven't been bullied into a situation by my record company, or by anyone, to go to the gym or get a boob job or use music dancers in my videos. I'm proud that I've managed to make a type of music that allows me to just be a musician and say what it is I want to say and not have to rely on anything else, and hopefully that can inspire young people."