Your Zotero Files
If you are using the Firefox plugin version of Zotero, by default your Zotero library is stored in the 'zotero' directory of your Firefox profile. The easiest and most reliable way to find your Zotero data directory is by clicking the “Show Data Directory” button in the Advanced tab of your Zotero Preferences window.
Syncing Your Data and Files
All of the item information, notes, and attachments imported into your Zotero collection are stored locally in this directory on your computer. If you would like to be able to access your collections from any computer connected to the Internet, then you must register with Zotero for an account and sync your data between your computer and Zotero's servers. Zotero provides 300MB of free storage.
Everything in your collections, including notes, links, and tags, will be saved to the server, except attachments.
After you have registered with Zotero, open Zotero's Sync preferences tab and enter your login information in the Zotero Sync Server section. Each time changes are made to your Zotero collections, Zotero will automatically sync your data. You can disable automatic syncing in the preferences window. You can sync manually at any time by clicking the “Sync with Zotero Server” button () on the right-hand side of the Zotero toolbar.
By default, Zotero will merge your local Zotero library with your library on zotero.org—any changes you make in one place will be applied to the other and on all other synced computers. If an item has changed in multiple places between syncs, you'll receive a conflict resolution dialog asking which version you'd like to keep. In the rare case that you want to completely overwrite your server library with the contents of your local library or vice versa, you can use the Sync Reset Options.
File Syncing with Zotero
Data syncing syncs library items, but doesn't sync attached files (PDFs, audio and video files, images, etc.). To sync these files, you can set up file syncing to accompany data syncing, using Zotero File Storage. Each Zotero user is given 300 MB of free Zotero File Storage for attached files, with larger storage plans available for purchase.
File Syncing with WebDAV
Another option for remote storage of files is to use a WebDAV service. Zotero does not provide support for third party WebDAV providers and when you set it up, you should make sure to use the "Verify Server" option to ensure that Zotero can successfully verify the WebDAV account.
One WebDAV service option is CloudMe, which provides 3GB of free storage. After you create your account at CloudMe, create a folder called zotero.
Then, in Zotero preferences, under "Sync", do the following:
1. select http:// (not https://)
2. type in webdav.cloudme.com:80/[user_name]/xios/Documents (your user name goes into the URL)
3. enter your CloudMe user name
4. enter your CloudMe password
5. click "verify server"