A toggle is a feature that allows you to switch between two different states or options. Toggles are often used in technology, computing and programming to provide users with the ability to change a setting or mode. They are also commonly found in user interfaces and can be implemented on websites to allow users to change the theme or layout of a page. A toggle can be activated by pressing the button or clicking the link to turn it on and deactivated by turning the switch off again.

When creating a website, a toggle can be used to enable or disable features which may not be appropriate for all visitors. For example, a website might include a toggle for disabling cookies or other tracking software which may be inappropriate for children or those who are concerned about their privacy. Toggles can also be used to allow or restrict access to content based on gender, age, location or other factors.

Feature toggles are a useful tool for managing feature deployment and rollout. Using feature toggles can help to reduce the time it takes for code to go through the CI/CD pipeline and can also improve the feedback loop for testing and debugging. However, like all powerful tools, it is important to use feature toggles with caution and ensure they are well managed in order to avoid creating a situation where the complexity of the features under control of a single toggle becomes unmanageable.

Toggles are especially valuable in a trunk-based development process as they allow for the easy merging and reconciliation of changes to the main source code branch. They can be an effective way of managing the risk associated with changing code that is already in production, and they can be particularly helpful when introducing new features to existing users as it can be easier to roll back any unwanted changes if needed.

A common use of toggles is to enable responsive web design, for example by enabling users to choose between a light and dark theme for a website. Toggles can also be used to switch between various layouts and display options based on screen size or device type.

When building a website, it is recommended to keep the number of toggles used to a minimum in order to avoid confusing and convoluting the user experience. It is also recommended that toggles are named in a meaningful manner and not used to manipulate the layout of a webpage as this can cause cognitive problems for users.

Savvy teams view the inventory of toggles in their codebase as a carrying cost and seek to minimize this by being proactive in removing toggles from the codebase once they have reached the end of their lifecycle. This can be done by adding a toggle removal task to the team’s backlog when a new toggle is introduced or even putting in place a system that will fail tests (or even refuse to start an application) if a long-lived toggle is not removed from the build at the end of its lifecycle.