You can choose to do a Sitewide Search, or search in All (the currently searchable) Online Collections*, or search in one online collection chosen from the dropdown, or in All Reading Room Collections, or search in one reading room collection chosen from the dropdown.

You can use Boolean operators (AND, OR, and NOT) to organise and sift through your searches. These produce more accurate and relevant results, allowing you to navigate through related results, while disregarding the unrelated.

AND / + e.g. Dublin AND Army / Dublin + Army
OR / | / , e.g. IRA OR Irish Republican Army / IRA | Irish Republican Army / IRA , Irish Republican Army
NOT / - e.g. IRA NOT Easter Rising / IRA - Easter Rising
( ) e.g. (Dublin AND Army) NOT IRA
“ ” e.g. “Civil War”

*See "What can you search here?"

A sitewide search includes the Resources, News & Events, most of the Reading Room Collections and the currently searchable Online Collections*:
Bureau of Military History (1913 - 1921)**,  The Collins Papers (1917 - 1922),  Irish Army Census Collection (12 November 1922 - 13 November 1922),   Maps, Plans & Drawings Collection (1702 - 2007),   The Irish Volunteer (1914 - 1916),  Oral Histories Project (20th Century),  Military Archives Image Gallery (20th Century),  Nominal Rolls (1921-1922),  An tÓglach Magazine (1918 - 1933) and Military Service Pensions Collection (1916 - 1923).

* Further collections will be added to search in the coming weeks and months.
** The Bureau of Military History - Witness Statements results include a link to search inside the PDfs for more detailed results.

The Reading Room Collections listed in the dropdown are searchable. If they are not in the dropdown they are not searchable.
The only Online Collections not currently searchable are Military Archives Image Identification Project (20th Century) and United Nations Unit Histories (1960 - 1982).