But consumers, he said, should not expect all information to be current or correct. For instance, the site listed Mr. Howe as the father of two; in fact, he is the father of three. It had also pegged him as Italian, but he is actually of Norwegian descent. (The system predicts likely ethnicity based on surname and is clearly imperfect.)

The home section, meanwhile, which listed such details as the year his house was built and its estimated market value, had incorrect information about his mortgage. “I don’t have a loan on my house anymore. It’s drawing on old data,” Mr. Howe explained. “That’s one I would absolutely go in and change.”

If a personal detail is corrected on the site, the new entry will appear with an aside noting the previous, incorrect entry, letting consumers see what they amended. Mr. Howe acknowledged that the system was fallible because Acxiom obtains information from many different suppliers, and the latest data is not always available in its databases. He said he couldn’t predict how Acxiom’s clients might react to a system that lets consumers update profiles and perhaps fictionalize them, or opt out altogether from Acxiom’s marketing database.

“What happens if a flock of people who are 45 decide to be 39?” Mr. Howe asked. “What happens if 20 percent of the American population decides to opt out? It would be devastating for our business.”

If past consumer behavior is any sign, the number of opt-outs isn’t likely to be high. For instance, Forrester Research reported this year that only 18 percent of Web users had activated an option in their browsers, called Do Not Track, that informs sites and ad networks that they don’t want their browsing histories tracked for marketing purposes.

“It’s a little bit of a risk,” Mr. Howe added of the opt-out provision. “But I feel it’s the right thing to do.”

It may be both the right and the timely thing. The new consumer site should help Acxiom get out in front of potential regulation — at a time when the company is about to introduce a more powerful consumer-targeting engine for its corporate clients that may well set off an outcry from privacy advocates. Last year, some members of Congress opened inquiries into the business practices of data brokers in light of an investigation by The New York Times.