Opera is a web browser for Windows, macOS, and Linux operating systems developed by Opera Software. It uses the Blink layout engine. An earlier version using the Presto layout engine is still available, and runs on FreeBSD systems. According to Opera, the browser had more than 350 million users worldwide in the 4th quarter of 2014. Total Opera mobile users reached 291 million in June 2015. According to SlashGeek, Opera has originated features later adopted by other web browsers, including Speed Dial, pop-up blocking, browser sessions, private browsing, and tabbed browsing.

Opera began in 1994 as a research project at Telenor, the largest Norwegian telecommunications company. In 1995, it branched out into a separate company named Opera Software ASA. Opera was first released publicly in 1996 with version 2.0, which only ran on Microsoft Windows. In an attempt to capitalize on the emerging market for Internet-connected handheld devices, a project to port Opera to mobile device platforms was started in 1998. Opera 4.0, released in 2000, included a new cross-platform core that facilitated creation of editions of Opera for multiple operating systems and platforms.

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