Balsamiq Mockups is a web tool that allows users to mock up different designs and ideas quickly and easily. Balsamic Mockups is similar to drawing mockups, but it is digital
Instant wireframing at your fingertips.
Whimsical includes a rich library of configurable elements like buttons, inputs, checkboxes, and more.
MockFlow is an online wireframe software that helps to design, collaborate (in real-time) user interface mockups for software and websites.
It is built for the purpose of providing a free and open-source GUI prototyping tool that people can easily install and use to create mockups in popular desktop platforms.
Mockingbird is an easy and fast way to make clickable wireframes and prototypes. Create and share clickable mockups of your website or application.