The BBC's iPlayer made its public debut in 2007
The BBC's iPlayer is to start offering high definition (HD) streams and downloads of some programmes.
It will mean improved picture quality on streams to web browsers.
For many users, it will be their first chance to view HD television, with Doctor Who, Kerwhizz, and Dragons' Den all slated for HD release.
The iPlayer has been a runaway success, with more than 387 million requests to stream or download since it launched on Christmas Day 2007.
BBC's head of digital media technology, Anthony Rose, who is responsible for delivering the next generation of BBC iPlayer, said the launch of an HD iPlayer was a significant milestone in improving video quality.
"Introducing HD streams enables users to enjoy BBC programmes in HD without a set-top box," he said.
The updated iPlayer also comes with a diagnostic tool that examines a user's internet connection and automatically switches the streaming options to give the best quality image.
The player will now also allow users to customise the size of their viewing window which, the developers say, is now nearly twice as good as the previous high quality format.
"The new adaptive bitrate technology and speed diagnostics page help optimise the viewing experience, while the resizable window gives users flexibility to switch between different quality streams, hopefully leading to a more satisfying experience overall," said Mr Rose.
The next three Doctor Who specials will all be in HD on the iPlayer
Danielle Nagler, head of BBC HD, said: "In the last month we've extended the channel hours to nine per day, refreshed the look, enhanced the range of programmes, and now our HD content will be available whenever and wherever the audience want it."
Other new features include a new internet speed diagnostics page, the full release of the new BBC iPlayer Desktop, and a cross-platform manager that will allow Windows, Mac, and Linux users to download BBC programmes, including those in HD.
At present, the new HD service, which also includes HD downloads of some programmes, is only available on the BBC iPlayer.
There are plans to roll out the HD streams to devices such as the Virgin Set Top Box and PlayStation 3, but no date has yet been set.