4oD currently offers programmes for 30 days after broadcast
Some of Channel 4's most popular shows like Shameless, Ali G and Father Ted are to be put online, allowing viewers to watch every episode free of charge.
More than 4,000 hours of the channel's archived content - about 10,000 programme titles - will be added to the 4oD catch-up service from July.
Other shows to be made available include Queer As Folk, Teachers, Brass Eye and Trigger Happy TV,
4oD currently allows viewers to watch programmes for 30 days after broadcast.
There will also be a selection of episodes from axed soap Brookside, featuring its "most important storylines", including the infamous body under the patio and the first lesbian kiss to be shown before the 9pm watershed between characters Beth Jordache (Anna Friel) and Margaret Clemence (Nicola Stephenson) in 1993.
"The addition of archived content to 4oD on channel4.com means we will be the only UK broadcaster to have all of our content available online," said Jon Gisby, director of future media and technology at Channel 4.
"We are extremely proud of the new and improved service and think the combination of fantastic content that's easy to find and view will prove a compelling service for all users."
US shows like Friends will not be made available online due to rights or legal issues, nor will Channel 4 News, as some bought-in news clips are only licensed to be shown up until midnight on the day of transmission.
The service will be made available to PC, Mac and Linux operating systems users on a free, streamed basis.
The BBC's iPlayer service currently offers programmes for seven days after they air.