Cambridge English Language Assessment, formerly called Cambridge ESOL, is the organization behind the Cambridge English exam suite as well as the IELTS exam, in collaboration with the British Council. It is a non-profit organization headquartered in Cambridge, England.
Cambridge English was established in 1913 and is associated with Cambridge University. When it was founded, Cambridge ESOL offered just one test, the CPE, which took 12 hours to complete. It was another 20 years before the second Cambridge English exam was introduced. The Cambridge exam suite has since expanded to include over a dozen tests, each specialized either for a particular type of learner (children, teens, etc.), by English level (beginner, intermediate, etc.) or by field (law, finance, etc.). The specialization of each exam is the main distinguishing factor between Cambridge English exams and other standardized English tests. Cambridge English is also distinct in that their exam certificates do not expire. Many English tests only count their scores as valid for 2 years after the test date.
Cambridge English participated in the elaboration of the Common European Framework of Reference (CEFR), a standard used across Europe to describe foreign language ability. All the Cambridge exams are aligned to the CEFR. Cambridge English cooperates closely with the British Council in managing the IELTS, and in the past decade has formed an alliance with the University of Michigan to develop English language testing in the USA.