• by Wendy Davis  @wendyndavis, April 14, 2010

Some Web companies have touted the use of Flash cookies as an alternative to HTTP cookies, largely because Flash cookies tend to be harder to delete and therefore, more persistent. But a new study by start-up Scout Analytics suggests that far more consumers now remove Flash cookies than even one year ago.

In a report to be published today, Scout Analytics says that around 7% of the users who receive its Flash cookies delete them within 30 days. That proportion is more than double the 3% of people who deleted Flash cookies last July, when Scout started examining the issue.

Scout arrived at those figures by examining Web traffic for 55 business-to-business sites that draw a total of around 180,000 users. The company, which helps sites analyze their visitors, only tracks people's behavior within particular sites. Scout doesn't track people as they surf the Web.

"Originally we used HTTP cookies to help with tracking, but found that they were being deleted," says Senior Vice President For Strategy Matt Shanahan. "So we moved to Flash cookies. But we found out there was a deletion problem there as well."

He says that Scout is able to recognize users who have deleted their Flash cookies in two ways. First, he says, many have registered at the sites Scout works with and sign in when they visit those sites. Second, Scout also identifies users based on their browser configurations -- which often are unique enough to serve as digital fingerprints.

Shanahan says the increase in Flash cookie deletions might be partly due to the newest version of Adobe, now in "pre-release," which offers a "private browsing" mode that automatically deletes such cookies at the end of a session.

Flash cookies initially were used to store people's preferences for Flash-based applications like online video players, but some companies began using such cookies for tracking in recent years.