Bootstrap is the front-end framework that began at Twitter as an internal tool called Twitter Blueprint.
Designers Mark Otto and Jacob Thornton developed the project at Twitter in 2010 to make the company’s internal interfaces more consistent. Before it existed, different teams used assorted libraries and conventions, creating repetitive work and uneven visual results.
The project gained contributors during Twitter’s internal Hack Week. It was renamed Twitter Bootstrap and released as open source on August 19, 2011. That public release allowed developers outside Twitter to use its CSS and JavaScript components for common interface elements such as buttons, forms, navigation bars, and responsive layouts.
Bootstrap’s association with Twitter explains why it is often confused with a company-specific branding system, but it became an independent open-source project. Later versions emphasized responsive and mobile-first design, helping make Bootstrap one of the most widely recognized web-development frameworks.