The Daily Telegraph may have had a team of 25 journalists working on the MPs' expenses - but within 10 minutes of the launch on Thursday afternoon of the Guardian's crowdsourcing application to examine them there were 323 people, almost all outside the Guardian, doing the same task.

The application itself was developed at breakneck speed: coding began on Thursday 11 June, and was complete - aside from ongoing bug fixing as people began using it - by 3.30pm Thursday 18 June.

In the application, at mps-expenses.theguardian.com, each MP's expenses and claims are presented as a set of images, and users can determine - and detail - what entries there are on a page, and decide whether the page is unimportant, interesting, "interesting but known" - such as a duck island - or worthy of investigation.

Within half an hour of the launch, more than 2,000 pages had been reviewed. Future additions to the application may include a "top analysis" ranking for those who have contributed most to sifting the pages - a task which the Telegraph's team, despite having a three-month lead, is not believed to have been able to achieve.

Simon Willison, the head developer for the application, says he had the idea of creating a "crowdsourced" approach to analysing the claims about six weeks ago. That gained clearer focus after a number of MPs, including Frank Field and Charles Clarke, put redacted versions of their claims online.

Because the claims were released as PDFs, the contents could be examined, though PDFs are not as easily searched as a simple text file - and the addition of redaction, to cover up identifying data, means that to create a database from the claims would require someone to look at each page.

"The risk was that we didn't know how it would be released, but we assumed it would be like that," said Willison. "And it was."

Parliament made it simultaneously difficult and easy to deal with the data, he said: "Easy, because the website with the expenses [which went live at 6am on Thursday morning] was excellent, so we could suck all the data off it in about 15 minutes." But the difficulty was that the PDFs were not in the expected form, leading to a scramble to find appropriate software that would be able to present them as required by the application - which was written in Django and uses Amazon's EC2 cloud computing service, both a first for a production-quality effort by the Guardian.

The unexpected PDF format and the need to feed the documents into extra processing led to a last-minute scramble as the entire quality assurance team for the Guardian's systems were allocated to testing the application on Thursday morning and lunchtime to iron out any obvious bugs.

"It's the first time we've ever knocked out an application in five days," said Matthew Wall, head of software architecture at Guardian News and Media.

Even as the app went live, 30 computers were still churning through the PDFs from the parliament website to turn them into a usable form, so that people can analyse them in forthcoming days.

The Guardian is not alone in attempting to "crowdsource" the analysis of the MPs' expenses released by parliament. Another is whathavetheyclaimed.com.