The service will be shut down on March 30, the company said on Wednesday. Yahoo is warning users to retrieve or delete their documents before that date.
Briefcase, which offered 30MB of online storage, was launched almost 10 years ago. However, "usage has been significantly declining over the years, as users outgrew the need for Yahoo Briefcase and turned to offerings with much more storage and enhanced sharing capabilities", the company said in a statement.
There are now many alternative online storage services to Briefcase. Notable rivals include Microsoft's SkyDrive, a Windows Live service that offers 25GB of free storage.
There are also signs that Google may be preparing a free online storage product called GDrive. Recent reports have pointed to a reference to GDrive in an online, recently updated file associated with its Google Pack bundle of free software, which includes Chrome and Picasa. The file text says that GDrive "provides reliable storage for all of your files, including photos, music and documents [and] allows you to access your files from anywhere, any time and from any device — be it from your desktop, web browser or mobile phone".