Ireland On-line was the first commercial internet service provider in the state. The company was formed in 1992 by Barry Flanagan, and was reported to have launched "Ireland's first mass-market Internet service" in January 1994. In 1997, the company was bought by An Post for IR£2.5m. Two years later, it was sold to Esat Telecom Group plc for IR£ 115m. A year later, Esat Telecom was taken over by BT Group plc. In 2002 Esat was rebranded Esat BT. In 2009 BT Ireland withdrew from retail telecommunications and transferred retail operations, along with IOL's former subscribers, to Vodafone Ireland.
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- Boyle, Pat (11 July 2002). "Rebranded Esat BT holds all Irish units". Irish Independent. Retrieved 18 December 2011.
- Apostolou, Natalie (23 July 2009). "Vodafone snaps up BT's Irish ISP customers". TelecomsEurope. Archived from the original on 21 April 2012. Retrieved 18 December 2011.