1Password 4 was created in 2012 and has not been under active development since 2014. It supports OS X Mountain Lion and Mavericks, so it has compatibility issues with recent operating system (OS) and web browser releases and won't be receiving updates in the future. Since we use 1Password to help us be more secure, it's important to stay up to date with not only 1Password, but also OS and browser updates, which contain important security fixes.
If you've purchased 1Password for Mac version 4, you're entitled to use it on all of your compatible devices indefinitely, and version 6 is a free upgrade. And if you'd like to always have the newest version, along with many other benefits, you can sign up for a 1Password.com membership. This works with macOS Yosemite, El Capitan, and Sierra, and supports the latest versions of major browsers.
If you're unable to upgrade, you can still use 1Password 4 in a limited fashion, bearing in mind the security risks, and that you may encounter some issues introduced over time:
Google is no longer providing Chrome updates on OS X Mountain Lion and older, and Mozilla has done the same with Firefox.
1Password 4 cannot connect securely to Chrome 58 or higher, as Google has changed their code signature as of May 2017, so 1Password 4 can no longer validate it. Upgrade 1Password/macOS, or disable the security check in Preferences > Advanced (not recommended).
Similarly, Mozilla's certificate for Firefox has been updated, and the old one is expired as of May 2017. 1Password 4 will not be able to verify the identity of the browser any longer. Upgrade 1Password/macOS, or disable the security check in Preferences > Advanced (not recommended).
While 1Password 4 has benefitted from many improvements we've continued to make in the 1Password browser extensions in recent years, future versions of the 1Password extension that we're working on will require 1Password 6 or later. These changes are needed to support the new WebExtensions standard being adopted (and soon required) by major browsers. And since the browsers automatically update extensions, eventually they will no longer work with 1Password 4 — once we're no longer allowed to use the current method (WebSockets) which will be deprecated and then removed completely from browsers later this year. The importance of staying up to date, both for security and to continue to get the most out of 1Password, cannot be overstated.
If you purchased a license from the AgileBits Store, click “Using OS X Mavericks or earlier?” on the 1Password Downloads page to download the version you need.
If you purchased through the Mac App Store, you'll need to install it from the "Purchased" tab in the App Store on your Mac with the Apple ID used for the purchase.
The 1Password extensions for each browser can be downloaded from the 1Password Browser Extensions page.