Sandwich shop web start-up nibbles at Google Jean-Baptiste Rudelle started his online advertising company in a spare room behind his wife's sandwich shop in Paris. The shop, Lilo, no longer exists. Luckily for the Rudelles, the company he founded, Criteo, may be the next billion-dollar technology IPO. Criteo has grown quickly from its sandwich shop origins in 2005. The advertising group now employs nearly 800 people, with offices in London, Paris and Palo Alto, California. Its technology works by showing customers adverts for a product they may want, based on their browsing history - known as retargeting in the industry. This practice is becoming more widespread among digital advertisers, and is fuelling an intensifying corporate competition to accumulate information about consumers. A Financial Times investigation recently revealed that individuals" personal information is often sold for mere pennies. Customers who are served more relevant ads are more likely to engage with them, says the company. Unlike most retargeting companies, however, Criteo charges only when someone clicks on an ad. This payment model has enabled it to secure a toehold in a market dominated by Google, according to Ian Maude, an online advertising specialist at Enders Analysis. "One of the ways that companies like Criteo have forced themselves in is by saying: you only pay if we deliver," says Mr Maude. Although other companies, including Google, operate clicks-only payment models, Criteo is one of the few whose entire business is based on it. The group has been profitable since 2008, but like most internet start-ups it declines to give an exact earnings figure. Talk of an initial public offering in New York this year is growing louder. "It's well known that when you are a public company it's easier to raise capital than when you are private - and it's cheaper," says Mr Rudelle, though the company declined to give a timetable for any potential IPO. Criteo raised €30m last year from investors including Yahoo Japan and SAP Ventures, valuing it at $800m. The company has reportedly hired JPMorgan to advise on its long-rumoured IPO, according to Bloomberg. Earlier this year, French publication JDN suggested that Criteo would raise between $270m and $400m through a float in New York. Criteo's software works by analysing everything it knows about a user, such as whether they recently looked at a product online but shied away from buying it at the last minute, then firing what it thinks is the most relevant ad at them. "We deal with those decisions in a flash of a second," says Mr Rudelle. We can predict in a very accurate way the likelihood that someone's going to click on that on the banner, which is a very difficult prediction - even more difficult than a weather forecast. Targeted advertising online is a crowded market. Google dominates online advertising in both display - the banners and videos dotted around websites - and search - the paid-for links at the top of search results. While Criteo's clicks-only model works for some businesses such as retail, it is less use for companies trying to boost brand awareness, according to analysts. "[Criteo's model] attracts different advertisers," says Mr Maude. It's more direct response, less brand orientated. Advertising only to customers who are potentially interested in your products has long been a pipe dream of the industry. In print and television, putting your adverts in front of the right customers was a mixture of art and guesswork, rather than data. In the online world, however, it is now more accurate than ever. Criteo says it has an advertiser retention rate of 97 per cent. It was this stat that persuaded Greg Coleman, formerly of Yahoo and Huffington Post, to join Criteo as president. "It's like having a software as a service model where nobody needs to sign a contract," says Mr Coleman on the retention rate. Taking on Google in their own backyard provides an opportunity for revenge for Mr Coleman, who spent nearly a decade being roughed up by the search company while he was at Yahoo: "To get beat up on a daily basis by Google was really not fun." About 40 per cent of the company's 800 staff are engineers. "This is probably what distinguishes us," says Mr Rudelle. We are geeks.