The Library of Congress is adding to its already large collections of digital material with the donation from Twitter of the entire digital archive of public tweets. This is a significant number of tweets – since Twitter commenced in 2006, billions of tweets have been created and over 50 million are sent every day.

The tweets are being recognised as important historic records which provide commentary on significant events in history, such as the Haiti earthquake and the Mumbai bombing. With the widespread use of Twitter, the digital archive will include tweets from people all over the world, including tweets posted by President Barack Obama on the day he was elected.

The Library of Congress holds more than 167 terabytes of web-based information and has been collecting web-based material since 2000. The Library leads the National Digital Information Infrastructure and Preservation Program and has a number of digital preservation partners around the world. The Twitter archive is also in keeping with the Library’s long tradition of gathering individuals' firsthand accounts of history. The full Twitter archive will not be posted online but selected tweets around various themes will be available.

Up until now, Twitter, has been focussed on the present. In another interesting development, Google has indicated that it is going to make the Twitter archive searchable for users. The replay feature will allow users to search tweets posted at any given time, with a timeline above the search results making it possible to zoom in on tweets by the hour or minute. Initially the replay feature will only cover the last two months, but Google aims to have the whole archive back to March 2006, searchable later this year.

Both these developments will enhance the value of tweets as records of major events and people’s reactions to them and as records of social history. Read more from the Library of Congress, Twitter and Google and on the BBC website.