Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for garage door monitoring. In one aspect, a method includes the actions of obtaining garage door status data from one or more sensors; generating first status information based on the garage door status data, the first status information indicating initial status of a garage door; generating second status information based on the garage door status data, the second status information indicating that a garage door opener has started an operation; generating third status information based on the garage door status data, the third status information indicating a time duration that the garage door opener has operated since the garage door opener started an operation; and determining current status of the garage door based on (i) the first status information, (ii) the second status information, and (iii) the third status information.