The word toggle means “pin passed through the eye of a rope to hold it in place.” In software, it refers to an on-off command (like the Caps Lock or Num Lock keys on a keyboard) that activates a function when flipped and disables it when flipped back. A toggle allows a developer to hide or enable features without changing the codebase.

In addition to enabling faster releases, toggles can also be used to defer feature development and testing, which would normally be done on code branches under more traditional waterfall development models. The advantage of using toggles for these processes is that the code that’s written remains in trunk, and the team can use the same workflow for both development and QA, rather than switching between branching and merging.

It’s best to keep the number of toggles in the code base as low as possible. This reduces the management overhead for the team and helps keep new features focused on solving real user problems. It’s also important to ensure that toggle labels clearly communicate what the switch does. This is especially important when the switch doesn’t contain text “on/off”. Often, this means that the team needs to make sure that the switch looks like a slider and utilizes other visual cues such as movement and color.

Toggle switches should also be named in a way that gives useful information about who wrote them, when they were written, and what they are used for. This information can be extremely helpful when the team is trying to debug a bug and understand why an older version of the code was producing a particular result.