A library catalogue tells you what material is held by that library. Most libraries have computerised catalogues which allow you to access the library catalogue via the Internet. This type of computerised catalogue is often referred to as an OPAC (Online Public Access Catalogue) or Web OPAC. To access a library catalogue via the Internet you will need to know it's URL, or web address.

There may be older library material which does not yet have a computer record, find out the coverage of the online catalogue you are using from a member of library staff.

A library catalogue traditionally has covered the print material in one library only. However, there are now catalogues which allow cross-searching of multiple catalogues at once, such as WorldCat which enables you to search across the catalogues of many major academic libraries, the British Library and the National Library of Scotland.

Usually you can not use the library catalogue to search for individual journal articles. However, there are now catalogues which also search other online databases. This 'metasearch' technology changes the role of the library catalogue into more of a portal into the range of print and electronic resources available for your research.

To fully exploit the range of services on a modern library catalogue you need to understand what you are searching and how to search effectively.