You can download Zotero on the Zotero download page.

When it comes to using Zotero, you have several options:

• You can use Zotero for Firefox, a Firefox extension. This is the original way of using Zotero, and it offers the most reliable operation along with all of the available features. In this case, Zotero is embedded within Firefox. Once installed (see instructions below), Firefox will display a Zotero “Z” button in the toolbar at the top of your Firefox browser window. Clicking on this button will open up the Zotero pane at the bottom of the browser window. You can also choose to have Zotero open in a separate tab. Note that Zotero for Firefox runs on your own computer and is not the same as the zotero.org website, which provides limited access to your Zotero libraries but does not offer the full functionality of the Zotero client.

• If Firefox is not your browser of choice, or if you do not want Zotero to take up space in your Firefox window, you can choose to use Zotero Standalone. Zotero Standalone is a separate, browser-independent application, but it is almost identical to the Zotero for Firefox extension. Because Zotero Standalone lives outside your browser, it cannot offer some advanced features, like automatic proxy redirection. Similarly, since Zotero Standalone does not have access to the cookies stored in your browser, it is sometimes unable to automatically import file attachments when websites are accessed through a web proxy.
  
  One of Zotero's most compelling features is its ability to scrape bibliographic metadata from websites with a single click. In order to do this, Zotero Standalone needs to communicate with the browser you are using, which can be done by installing one of the Zotero Connectors:
  • Chrome, Safari, or Opera connectors can be installed by following the respective download links under the Zotero Standalone download button on the page linked to above.
  • Firefox can also be used with Zotero Standalone, using Zotero for Firefox. The Firefox extension is somewhat unique, because, while it is a full-featured Zotero application, it will automatically act as a Connector for Zotero Standalone if Zotero Standalone is open.
  • One-click scraping into Zotero Standalone from other browsers is possible using the Zotero Bookmarklet; however, this method is more limited (e.g. you will not see the Zotero URL bar icon and some pages will not be scraped).

• If you do not wish to (or cannot) install extensions or software on your computer, you have the option of using the Zotero bookmarklet from (almost) any browser, including mobile/tablet browsers. In this case, clicking on the bookmarklet will save the items directly to your online library at zotero.org. This allows you to easily add items to your library from any computer without the need (or ability) to install software. While this is convenient, you cannot currently control which collection the scraped item ends up in. It will simply go into the root of your library. Additionally, not all websites that are supported by the Firefox extension or Chrome/Safari/Opera connectors can be scraped using the bookmarklet. Finally, this option will not allow you to use Zotero's word processor plugin.

• If you are looking for a way to carry Zotero around on a USB drive, take a look at the Zotero with Portable Firefox setup.

• To install the Zotero Firefox extension, visit the Zotero download page with Firefox and click the red “Zotero for Firefox” button on the left. If a box appears above the web page with “Firefox prevented this site (www.zotero.org) from asking you to install software on your computer.”, click the “Allow” button. Then click the “Install Now” button in the “Software Installation” pop up window (the button may be grayed out for a few seconds) and restart Firefox after the installation has completed. You should now see the Zotero “Z” icon in the toolbar at the top of your Firefox browser window.

• To install Zotero Standalone, visit the Zotero download page and click on the red “Zotero for {Your Operating System}” button on the right. Your browser will download the setup file, which you would then use to install Zotero just like any other application on your computer. Make sure to also add the appropriate Zotero Connector for your browser (see buttons under the Zotero Standalone button) to enable one-click metadata scraping from websites.

Video by the Harvard Kennedy School Library

Both Zotero for Firefox and Zotero Standalone should be updated automatically by default. However, you can always manually install a new version of Zotero over your existing version without losing any data.

By default, Firefox checks periodically for updates of installed extensions, including Zotero, and applies the updates automatically when you restart the browser. If this isn't happening for you, see Updates Not Detected.

Zotero Standalone checks for and installs new versions automatically.

For general installation help, see Installation Instructions above.

See Updates Not Detected.

See No Toolbar Icon.

Try the following steps:

1. Restart Firefox completely and try the installation again.
2. Clear the browser cache and try again.
3. Right-click the “Zotero for Firefox” link and save the Zotero XPI file (e.g. “zotero-4.0.24.xpi”) to your computer. Then drag the XPI file onto a Firefox window to install it.
4. Download the Zotero XPI file from a different browser (e.g., Chrome, Safari, or Internet Explorer) or download it from a different network — or have someone else do so — and transfer it to your original computer (via email, Dropbox, a flash drive, etc.). Then drag the XPI file onto a Firefox window to install it.
5. Restart your computer and try again.

You can also review Mozilla's documentation for add-on installation errors.