San Francisco - Twitter was born in 2006 as a stream of SMS text messages. Before going public in 2013, it's now revelling in images.

The company tweaked its design Tuesday to favour image- and video-sharing by showing visual media directly within the Twitter timeline. Users previously had to click on a tweet to view the embedded multimedia.

Although the change does not affect the basic mechanics of how content is shared, it will likely alter the feel of Twitter, which long clung to its roots as an 140-character, text-based service invented in an era before smartphones existed.

As Twitter prepares to go public in a matter of weeks, the change will also present Twitter's advertisers with more opportunities to get attention-grabbing ads in front of users - leading to more revenue for the company.

Twitter has long acknowledged that pictures and video are some of the most often shared content in social media.

The most re-circulated tweet in Twitter history, for instance, was a picture sent from President Obama's account on Election Night in 2012. Three words - "Four more years" - captioned a photo of Barack and Michelle Obama embracing the moment the president declared victory.

"These rich Tweets can bring your followers closer to what's happening, and make them feel like they are right there with you," Michael Sippey, Twitter's vice president of product, said in a short blog post Tuesday. "We want to make it easier for everyone to experience those moments on Twitter."

Twitter's changes served up another reminder that social media remains one of the most hotly contested arenas in the technology sector.

Facebook made changes to its layout and newsfeed algorithms this year to more heavily promote visual content. It also acquired Instagram for $1 billion last year and has recently begun showing ads on the picture-heavy social network.

Earlier on Tuesday, Google Inc unveiled new features that let users publish slick home videos to its Google+ social network - a veiled assault on Twitter's Vine app and Facebook's Instagram, which support video-sharing.

Twitter's new look immediately drew mixed reactions from some of the tech digerati and early adopters, including many who predicted the more visual look would appeal to newcomers who might find Twitter's stream of rolling text confusing.

But Mathew Ingram, a writer at GigaOm, said Twitter was "in danger of suffering from what some call the MySpace effect (an excess of ads and gaudy images)" precisely because Twitter's old guard was accustomed to streamlined text.

"Will the number of enthusiastic advertisers make up for the number of irritated and/or overwhelmed users?" Ingram wrote.

Others, like Aaron Levie, the wise-cracking chief executive of file-sharing company Box, took advantage of the new design to simply point out how different Twitter felt.

Levie tweeted: "People on Twitter right now." In the same tweet, he appended a screenshot of two characters from the film Jurassic Park, their jaws slack with astonishment.