Inform is a design system for interactive fiction based on natural language, a new medium of writing which came out of the "text adventure" games of the 1980s. It has been used by many leading writers of IF over the last twenty years, for projects ranging from historical reconstructions, through games, to art pieces, which have won numerous awards and competitions.

Inform's educational users span a uniquely wide age range, from primary schools to graduate computer science classes. Although Inform has also been used for commercial commissions, in architecture, in the games industry and in advertising (most recently for a major 2014 product launch), its primary aim is to help and to encourage individual writers to express themselves in a new medium. In a single evening with Inform, it's possible to write a vignette and publish it as an interactive website, playable on any browser.

The Inform project was created by Graham Nelson in 1993 and first came to the Macintosh Programmer's Workshop in 1995, and is now available as an app. It combines the core Inform software with full documentation, including two books and nearly 500 fully working examples. Connecting to the Inform website, it can automatically download and update extensions from a fully curated Public Library used by the world-wide Inform community. The app offers richly detailed indexing of projects and scales from tiny fictions like "Kate is a woman in the Research Lab" right up to enormous imaginary worlds whose source text runs to over 3 million words. Features for automated testing, packaging and releasing round out a fully-featured development environment for IF.

Inform is free, with no strings attached. What you make with it is yours, to publish on your website, sell, or give to your friends. There's a vibrant community of users who welcome newcomers (and the app will help you find a high-traffic forum for discussions). Lastly, Inform is continuously maintained and developed. All bug reports are examined and acted on (and the app will show you how to post them).