OLB is a binary file that contains OLE object library. OLB format is used by Microsoft Office application. Some advanced documents, presentations, or spreadsheets may not display contents correctly if have no access to related OLB files.

OLE technology allows embedding or linking objects from different documents to documents or applications. Any change introduced to the original source will be reflected int the document that references such object. OLB library also allow creation of more advanced objects using any programming language.