Begun as a technical writing consulting firm, O’Reilly started publishing books about programming and computer technology in 1984. These books, known for the woodcuts of animals on the cover, became such a pervasive feature of the internet revolution that when, in 2000, the cover of Publisher’s Weekly declared, “The Internet Was Built with O’Reilly Books,” no one could take exception to the claim. In 1992, O’Reilly published the first popular book about the internet, Ed Krol’s groundbreaking Whole Internet User’s Guide and Catalog, which helped to popularize the World Wide Web when there were fewer than 200 websites. O’Reilly went on to create the first commercial web portal in 1993, the Global Network Navigator (GNN). GNN was the first site on the World Wide Web to support advertising. GNN was sold to AOL in 1995, one of the first big transactions of the dot-com boom.

O’Reilly was long recognized for the conferences and summits it organized. In 1997, the firm launched the Perl Conference to raise the profile of the Perl programming language. Then, in 1998, realizing the need to tell a broader story about the role of free software in the internet economy, O’Reilly invited notable leaders of various free software projects to a meeting. At this gathering, the group formally agreed on a new term to tell their combined story—“open source software”—so the meeting became known as the Open Source Summit. The O’Reilly Open Source Convention, also known as OSCON (and which included the Perl Conference), was one of O’Reilly’s flagship events.

In 2003, after the dot-com bust, O’Reilly’s corporate goal was to reignite enthusiasm in the computer industry. Dale Dougherty, an executive at O’Reilly, coined the phrase “Web 2.0” during a brainstorming session. This then became the name for the influential Web 2.0 Summit run by O’Reilly and TechWeb (formerly CMP Media). Web 2.0 framed what distinguished the companies that survived the dot-com bust from those that died, and identified key drivers of future success, including what's now called “cloud computing,” big data, and new approaches to iterative, data-driven software development.

The most recent events hosted by O’Reilly included the Strata Data Conference, the AI Conference, the Velocity Conference, the Software Architecture Conference, and the invitation-only Foo Camp (a “Friends of O’Reilly” unconference). In 2016, the company produced 19 conferences across the US, Europe, and Asia. In early 2020, the coronavirus disease (COVID-19) pandemic caused a shutdown of in-person conferences all around the world, and O’Reilly made the difficult decision to close down the conference portion of the business. (The Foo Camp series is expected to continue.) O’Reilly founder Tim O’Reilly continues to be a highly sought-after international speaker, giving keynotes on technology and culture and interviewing some of the world’s top technology leaders.

In 2004, the company named the “Maker movement” with the launch of Make: magazine, and in 2005, Maker Faire. As recently as 2019, the flagship Maker Faire in San Mateo, California, drew over 130,000 attendees, and other Maker Faires around the world have collectively drawn millions. In 2012, O’Reilly spun out the Make: properties into a separate venture-backed company, Maker Media, headed up by former O’Reilly executive and Make: founder Dale Dougherty.

In 2001, O’Reilly launched Safari Books Online, a subscription-based service providing access to ebooks as a joint venture with the Pearson Technology Group. In 2014, O’Reilly acquired Pearson’s interest in the joint venture, rebranding it O’Reilly online learning, which is now a wholly owned subsidiary of O’Reilly Media, based in Sebastopol, California. The largest and most successful learning solution for technical and business topics available on the internet, O’Reilly online learning has millions of users through B2B, consumer, government, and library channels. Customers include Silicon Valley companies like Google, Amazon, Netflix, and Tesla as well as giants in industrial, banking, and other sectors.

The firm is headquartered in Sebastopol, California, with additional offices in Boston, Massachusetts; Farnham, UK; Tokyo, Japan; and Beijing, China.