Glitch

 Glitch  (formerly Gomix, HyperDev before that) is a tool allowing you to quickly prototype web applications in a complete IDE with built in version control, sharing, custom domain support, and more.

It works similar to a CodePen or Gist but it allows you to write a Node.js-based server to complement the front end.

It's made by Glitch Inc, formerly known as Fog Creek Software.

IndieWeb Examples

 * made the authorship algorithm testing tool https://sturdy-backbone.glitch.me/ using Glitch
 * has made several projects using Glitch
 * 🕸💍, an IndieWeb webring. (Source on Glitch).
 * A standalone IndieAuth authorization endpoint, ported from selfauth. (Source on Glitch). 2018-03-12 announcement.
 * A Micropub endpoint that can create posts on NeoCities sites. (Source on Glitch). 2018-03-12 announcement.
 * Kapowski, a micropub client for posting animated GIFs. (Source on Glitch). Kapowski has been ported to PHP and moved from Glitch. Archived Glitch code

Other Uses
Glitch is a common enough word that it has been used to mean other things:
 * Glitch game by makers of Slack
 * HTML slideshow a poorly responsive slidedeck, not recommended for use