Why does TextExpander force me to enable Accessibility access? (Mac)

For privacy reasons, Mac OS X does not allow third-party applications (such as TextExpander) to log keystrokes, unless Accessibility access is checked for TextExpander and TextExpander Helper in the Security & Privacy system preferences.

It can be tricky to grant this access to TextExpander Helper on some Yosemite systems. If Yosemite presents an alert about TextExpander Helper and Accessibility every time you launch, see this article for more information.

Or go directly to this step-by-step solution.