A web widget is a portable chunk of code that can be installed and executed within any separate HTML-based web page by an end user without requiring additional compilation. They are derived from the idea of code reuse. Other terms used to describe web widgets include: gadget, badge, module, webjit, capsule, snippet, mini and flake. Web widgets usually but not always use DHTML, JavaScript, or Adobe Flash.

Widgets often take the form of on-screen tools (clocks, event countdowns, auction-tickers, stock market tickers, flight arrival information, daily weather etc).