Readers will be able to search through around 25 million pages of material next year without having to visit the library in London or pay any fee.
Microsoft initially is investing US$2.5 million (-2.1 million) in the project, but both sides say there are plans to digitize more titles in the future.
A plan by search engine Google _ a rival to Microsoft's MSN search engine _ to upload its own digital library has been dogged by complaints from publishers that their copyrights were being infringed.
Mindful of that controversy, Microsoft and the British Library stressed that they would be choosing books only from the older end of the library's vast collection of 13 million titles, as these have long fallen out of copyright.
Despite the fierce rivalry between the two digital companies, the library said its deal with Microsoft was not exclusive _ the scanned books would be posted on the British Library's own Web site, currently freely searchable through Google.
"This is great news for research and scholarship, and will give unparalleled access to our vast collections to people all over the world: They will be available to anyone, anywhere and at anytime," the British Library's Chief Executive Lynne Brindley said in a statement, AP reported. V.A.