Techniques for input session between devices based on an input trigger are described and may be implemented to enable a first device (e.g., a mobile device) to serve as an input device for a second device. Generally, the described implementations enable multiple different input triggers to be utilized to trigger an input session between devices, such as for enabling proximity-based input (e.g., stylus input, touch input, etc.) to a first device to be provided as input to a second device.