Twitter's first revamp in four years is major overhaul
Twitter has undergone its first major facelift which aims to provide a rich multi-media experience for its 160 million users.
The redesign aims to make it easier for users to check out photos and video.
As Twitter competes for advertising dollars, it is also seeking to ensure people stay on the website for longer and return more often.
Twitter.com now spreads information over two "panes" instead of over one page.
One pane or panel is devoted to the 90 million messages or tweets posted on the site every day.
The other features images within the text. Until now, most links to photos and video have been displayed on other websites or browser tabs.
The firm said deals had been made with 16 photo and video sites including YouTube and Flickr to have their visual content embedded on the site.
"You can now take a simple short tweet and get more context and information in less time," Evan Williams, Twitter's chief executive and co-founder, told BBC News.
"We liked the old Twitter but we thought we could make it better. There was a lot buried underneath Twitter and now we are bringing all of that to the surface."
During the launch at Twitter's headquarters in San Francisco, Mr Williams revealed that 370,000 new users sign up every day.
The benefits to advertisers seem clear if users end up spending more time on the site and coming back more often.
The site recently introduced what are known as promoted tweets to allow advertisers such as Starbucks and Best Buy to sponsor tweets that show up when a user searches for certain key words on the service.
"What advertisers on Twitter are looking for is engagement, " said Mr Williams.
"This will improve that out of the box."
He gave as one example the possibility of a movie studio advertising a new film now being able to display a video trailer on Twitter.com.
As well as focusing on its own future growth, Twitter has developed a thriving eco-system for a number of start-ups that have built apps to make Twitter easier to use.
The fear is that if users spend more time on Twitter.com, it will hurt businesses like TweetDeck, Brizzly and Seesmic.
But Mr Williams disagrees.
"I don't think it sounds the death knell," he said. "We have made it pretty clear that third-party clients are important and add a lot of value to Twitter.
"That doesn't mean we are not going to improve the interfaces we own and control. Our goal is to make people more happy and engaged Twitter users."
Analysts and industry watchers attending the launch were largely impressed by the new Twitter.com.
"It is one of the slickest web applications I have seen in a long time," said Ben Parr of social media blog Mashable.com.
"They have made a very complete product and clearly thought this through very well."
MG Siegler of news blog TechCrunch.com agreed.
"This is the single biggest change they've ever made to the site since its initial launch," he said. "That's going to rub some people up the wrong way, but overall, my initial impression is that this is definitely an upgrade in pretty much every way."
Forrester Research social media analyst Augie Ray called the announcement a "significant evolution".
"The long-term effects could be substantial as Twitter focuses on powering growth by improving Twitter consumption," he told the Los Angeles Times.