By Dan Mitchell
September 4, 2013

FORTUNE — People who were 13 years old in 2006 are 20 now. Many of them no doubt would like to erase much of their online histories, especially the stuff they wrote on Twitter in their early-teen years: say, somebody who’s now a fan of 2 Chainz, but who seven years ago tweeted over and over again about how much they loved Fall Out Boy’s “Dance Dance.”

Too bad, because those tweets from the past are all accessible, along with every other tweet ever written since Twitter launched in 2006. The social-media indexing and analysis firm Topsy announced on Wednesday that it had indexed every tweet from the beginning — in all, about 425 billion pieces of content including pictures and pages linked from tweets. Before now, the index had reached back only to 2010.

The service is free. Users can do all kinds of things with it, such as narrow time parameters and graph results. Topsy’s algorithms allow ranking in terms of the number of retweets and the popularity of a particular Twitter user.

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Marketers and social scientists will no doubt find ways to make use of all that data that haven’t even been thought of yet — even the really old stuff, which at first blush might not appear to be particularly valuable. But data researchers go back a lot further than seven years all the time to study things like car-buying habits. The older Twitter gets, the more valuable the data will be for studying things like consumer sentiment or reactions to politicians.

Topsy makes most of its revenue from selling access to high-end, more granular data-analysis tools which include things like breaking down tweets by geographic origin or comparing terms. Subscribers pay a minimum of $1,000 a month for those services.

Good news, by the way, for Fall Out Boy: The band’s name has been tweeted 273,000 times in the past 30 days.

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