# Feature detection

• Feature detection is checking if a browser supports a feature or if a feature is enabled. If not, provide a form of fallback.
• Modernizr is probably the most popular library for feature detection
• Some common features to check for are touchevents, geolocation, localstorage...

# Feature inference

Feature inference is when you assume one feature exists because another one exists. This is bad practice because you can never be 100% sure.

# UA string

UA is a string text of data that each browser sends and can be accessed with navigator.userAgent. This contains info about the browser environment.