[2] The company was founded in September 2011 and has raised $315 million in venture capital funding as of 2021, at a valuation of $1.7 billion.

[1][23] In 2013, CircleCI suffered a major data breach due to its provider MongoHQ, but was able to quickly respond and replace its security keys, resulting in almost no lost customers.

[30] CircleCI supports Go, Java, Ruby, Python, Scala, Node.js, PHP, Haskell, and any other language that runs on Linux or macOS.

[4] CircleCI's target deployment environments include Amazon Web Services, Heroku, Azure, Google Compute Engine, Docker images, and virtual Linux, Android, Windows, or macOS machines with VMware.

[36] The proprietary configuration syntax introduces vendor lock-in, meaning that switching CI services requires rewriting the pipeline.