Items in Zotero libraries can be organized with collections and tags.

“Collections” allow hierarchical organization of groups of items, in advance of adding items to your library. Item may be placed in multiple locations (sub-collections) in your library collection. Items may then be retrieved by “drilling down” into the hierarchy.

“Tags” (also called “keywords” in other contexts) allow for detailed characterization of an item, and have the unique advantage of allowing the formation of ad-hoc collections after adding items to your library (e.g., one can use tags to locate items tagged “Sumarian” + “history”, and so on.)

Tags are portable, but collections are not: copying individual items between Zotero libraries will transfer their tags, but not their collection placements. Both organizational schemas have unique advantages. Experiment with both to see what works best for your own workflow.

Screencasts
Collections
Tags	Tag Selector Box

Click the “New Collection…” button above the left column (or right-click on “My Library” and choosing “New Collection…”), and give a name for the new collection. The new collection will appear as a folder inside “My Library”. Subcollections can be created by dragging and dropping a collection onto another collection, or by right-clicking an existing collection and choosing “New Subcollection…”.

To assign items to a collection, select them in the center column and drag and drop them onto a collection. New items are automatically saved into the selected collection.

It is important to understand that items can be assigned to multiple collections, and that doing so does not duplicate the item. In this sense collections are more like iTunes playlists than physical folders in a filling cabinet. When a collection is selected, the center column shows the items in that collection. “My Library” always shows all items.

By default, items added to a subcollection do not automatically appear in the parent collection(s). This can be changed with the “recursiveCollections” hidden preference. To find the hidden preferences enter “about:config” (without the quotes) in the URL address bar and (if using the Firefox plug-in) agree to be careful. Enter “Zotero” in the search field. Then, scroll to the “extensions.zotero.recursiveCollections” line. Do a mouse right-click, then “toggle” the value, which will change to true. Close the modal window. (The change is saved automatically.)

To move an item from a parent collection to a subcollection, simply 1) expand the collection to display the subcollection(s) but do not open them; and 2) from the parent collection, drag the items from the center column into the desired subcollection. If you do not want to keep the item in the parent collection; it should still be highlighted in the center panel. Pressing the delete key on the keyboard will remove it from the parent collection but it will remain in the subcollection.

Right-click on the collection (control-click on OS X) and choose “Rename Collection…”, and provide the new name.

Right-click on the collection (control-click on OS X) and choose “Remove Collection…”. Removing a collection does not delete the items in the collection.

Select the items in the center column and press the Delete key (Backspace on OS X). You can also right-click the selected items (control-click on OS X) and select “Remove Selected Item[s]”. This only removes the items from the selected collection, not from “My Library” or any other collections.

Note that when “My Library” is selected, pressing the Delete key (Backspace on OS X) will prompt you to delete the item. Deleted items are moved to the Trash, and removed from all collections.

When a collection is selected, you can delete items by pressing Ctrl-Delete (Cmd-Delete/Backspace on OS X). Alternatively, right-click (control-click on Macs) the selected items and choose “Delete Selected Item[s] From Library…”.

To see all the collections an item is in, select the item and then hold down the Option (OS X), Control (Windows) or Alt key (Linux). Keep the key pressed. After a brief delay, this highlights all the collections that contain the item.

Items that are not in any collection can be found in the “Unfiled Items” folder found under “My Library”. This folder can also be selected by right-clicking (control-click on OS X) “My Library” and selecting “Show Unfiled Items”.

The tag selector is located at the bottom of the left column. It shows all the tags that have been attached to the items shown in the center column (to show all the tags present in the library, click the multi-color button and select “Display All Tags in This Library”). By selecting one or multiple tags in the tag selector, only those items carrying the selected tags are shown in the center column. Clicking a selected tag again will deselect it. To deselect all tags at once, click the multi-color button and choose “Deselect All”.

The filter box at the bottom of the tag selector can be used to search tags. Only the tags containing the search string are shown.

The tag selector allows tags to be globally renamed and deleted. To rename a tag across all items, right-click the tag (control-clicking on OS X) and choose “Rename Tag…”. To delete a tag from all items, right-click the tag and choose “Delete Tag…”. To assign a tag to multiple items at once, drag a selection of items from the center column onto a tag in the tag selector.

To add a tag to an item by hand, select an item in the center column. Then select the “Tags” tab in the right column and click the “Add” button. Name the tag and press Enter. You can rename a tag by clicking on it, and delete it with the minus-button. Once you have added the tag it will also appear in the tag selector in the left column.

When items are saved to a Zotero library via a web translator, tags are sometimes automatically attached. For example, OPAC library catalogs provide subject headings for their records, which are saved as Zotero tags. Automatic tags behave the same as manually added tags.

Automatic tags can be hidden from the tag selector by clicking the multi-color button to the right of the tag selector's Filter field and deselecting “Show Automatic”. To prevent Zotero from adding automatic tags, uncheck “Automatically tag items with keywords and subject headings” in the “General” tab of the Zotero preferences.