Responsive or adaptive sites react to fit the screen size the site is viewed on. Moves towards responsive have been made by news outlets including Channel 4 News, BBC News, the Guardian and local titles the Shropshire Star and Express and Star.
Metro also today announced the launch of a digital edition app for Android, which will be released "within days", and a Kindle Fire app being launched "in time for Christmas".
In a briefing this morning, Metro's product development director, Jamie Walters, said the title is the first UK news site to deliver swipe functionality within a responsive site.
"We've taken app functionality and applied to browser product," he explained.
Walters said Metro readers could expect "enhanced social sharing and push notifications", and said the development team is also working on "personalisation" so that in time they can offer readers the possibility of creating a sports, showbiz, or 'guilty pleasures' edition.
Metro.co.uk is also moving to Facebook comments and to using WordPress as its CMS.
Metro, which launched in 1999 as a free morning pick-up newspaper and now has around 80 editorial staff, is investing in products for mobile devices in response to a changing audience, editor Kenny Campbell said during the briefing.
The "mobile-first strategy" is an extension of the fact that Metro has always considered the title a "mobile product" long before the release of smartphones.
"Our print offering which launched 13 years ago was the original mobile commuter product," Linda Grant, managing director of Metro, told the briefing, with Metro providing concise content suitable for consuming on the move.
And while there is increasing investment in mobile devices as the title moves to "where consumers are going and anticipating their needs", as Grant explained, the newspaper is still key.
"Print is still an incredibly important part for both consumers and advertisers," Scott told Journalism.co.uk.
'Urbanites' increasingly mobile
Metro is "about engaging urbanites", Grant said, reaching the audience during a "rare spot of available downtime".
Bryan Scott, marketing and communications director, added that urbanites are "mentally never still, physically on the move, continually doing more, always creating, always connecting, and looking to progress".
Metro has been working with the Future Foundation to gather market research. One of the terms the foundation uses to describe how urbanites behave is ‘smart boredom’. “It's really important that we capitalise on this," Scott said, with Grant adding that 'smart boredom' is an "opportunity for Metro".
And with the proliferation of smartphones and tablets among urbanites, Metro has already found some success on mobile devices.
Metro has had a total of 1.2 million downloads of its iOS apps, according to figures shared by the title today, and is adding an Android digital edition which is "going live in next couple of days".
More than 500,000 people have subscribed to the free apps, and there are currently 406,000 monthly users and 60,000 daily users of the digital editions.
Email alerts also demonstrate audience behaviour, with half of Metro marketing emails being opened on mobile devices.
Smartphones and tablets are "complementary" to the print product, Scott explained, with interactive puzzles launched by the title an example.
A new 'philosophy'
Walters added that the new mobile products, including the responsive site, are part of a new "philosophy" based on "brand and customer insight" coming out of Metro research.
In addition to a focus on mobile, Metro is also adopting "user-centric design and UX" and is aiming for a "consistency of experience across products".
Walters said: “You feel at home and know your way around” whether reading the Metro in print, desktop, tablet or mobile.
Another focus is on "the conversation", with social sharing an important component and after trialling Facebook comments on its blog, Metro is rolling it out across Metro.co.uk.
Metro is also responding to early indicators that a story will go viral. In the case of a story headlined 'Woman jailed after drunkenly stealing ferry and claiming she was a pirate', early analytics showed a high level of social sharing which resulted in Metro posting the story to its Facebook page and resulted in 25,000 'likes'.