Google said Thursday it has added a feature to its news section that allows users to customize it according to their interests, while Yahoo said its users could access customized news headlines on their cell phones.

said its users could access customized news headlines on their cell phones.

As RSS feeds become increasingly popular, news sites are battling it out to stay relevant and retain customers. It’s not just Internet companies that are looking at customization. Even established news organizations like Reuters consider personalization crucial to raising revenue.

“It engages the consumer in a greater way,” said Jupiter analyst Niki Scevak.

Google’s stock closed down $1.37 to $179.98 while Yahoo fell $0.41 to $31.91. As a group, tech stocks rose Thursday on the strength of increased optimism about chip sales.

As web sites and blogs compete for readers’ time and attention, personalization is central to getting users to come back. Microsoft is testing its news aggregation service, Newsbot, on the MSNBC news site. Yahoo’s My Yahoo, which is capable of integrating RSS feeds, is probably the most advanced offering in the space.

Google’s attempt at customization is a rather minor one, according to Rafat Ali, publisher and editor of paidcontent.org, a news site covering digital content. “At this point, everyone’s taking baby steps into [personalization],” he said. “In the industry’s view, they don’t know where this is going. It’s difficult to monetize something like a news search.”

It’s not impossible, but difficult because of the possible consequences. Google generates the bulk of its $3.1 billion in revenue from advertising, but commingling advertisements with someone else’s news content is a controversial subject, and one that Google has stayed away from so far. Even if it chose to monetize news search, it would only be able to go so far.

“The amount of money you can make is quite limited,” said Mr. Scevak. “When you’re searching for news, that is a lesser value to the advertiser. It’s simply that activity is less valuable than other forms of search [such as purchasing].”

The Mountain View, California, search giant, which is certainly not short of resources, is obviously just testing the ground here. The settings for the customized Google news page will be stored on the user’s computer, said the company. Compare that with Yahoo’s customized news service, which allows registered users to access their account from any computer, and now cell phones, too.

Mr. Ali said he believed news search was primarily a test bed for general search, given that what could be accomplished in a news search could also be done with search as a whole. If so, the experiments didn’t help the stock of either company.