A toggle is a switch that enables a user to update preferences, settings or other types of information. When used effectively, this simple user-interface component can have a big impact on the usability of your site or app. When in doubt, opt for a toggle over a checkbox or other UI element when users need to choose between two opposing states. When using toggles, ensure that they are easy to understand by providing clear labels, standard visual design and immediate results.
A toggle is the right control to use when a user needs to change system settings or preferences (i.e. states of system functionality). They are also the preferred control to use on mobile where space is limited because they occupy less screen real estate than two radio buttons. Toggles are not suitable for choosing yes/no options, as these require a more complex decision-making process.
The word “toggle” originates in 18th century English for a pin passed transversely through an eye or loop in a rope to fasten it. It is also used for a sliding fastener like the toggle on the lid of a pot. Today, the term is mostly found in computer technology to describe software switches that enable or disable a particular function. For example, the Caps Lock and Num Lock keys on a keyboard are toggles that turn specific functions on or off.
When using toggles, it’s important to consider color as a signifier of state change. Use high-contrast colors to make it easy for users to distinguish the current state of a toggle. Also, be mindful of societal and cultural implications when selecting colors for toggles. For example, red can have negative connotations in some cultures and may be counterintuitive to use as a state-change indicator.
As with all UI components, it’s vital to test toggles thoroughly. Aside from testing the configuration that will be live in production, it’s often wise to test a fallback configuration where all toggles are flipped Off. This helps prevent surprise regressions in future releases if a toggle is unexpectedly flipped On by accident.
Many teams manage their toggle configuration via static files. While this approach is simple enough it can become cumbersome once you reach a certain scale. It requires the re-deployment of code to modify a toggle, which can slow down the CI/CD process and the all-important feedback loop. In order to solve this problem many teams opt to move their toggle configuration into some type of centralized store, usually an existing application DB. This is typically accompanied by the build-out of some form of admin UI that allows for dynamic in-memory re-configuration of feature flags.
Savvy teams view their toggle inventory as inventory that comes with a carrying cost and seek to keep this overhead low. As a result, they are proactive about removing toggles that are no longer required. Some teams even set expiration dates for their toggles and create test cases that fail when a toggle is still active after the expiration date passes.