The EU decides its own common standards through many regulations and directives. But most often the EU just refers to the standards established by European Standards Organisations like CEN, Cenelec and ETSI. This delegation of more technical legislative power is based on Directive 98/34 EC.

CEN is the more general European Committee for Standardization with 13,425 established standards.

Cenelec is the European Committee for Electrotechnical Standardization with 21,343 standards.

ETSI is the European Telecommunications Standards Institute with 5,287 standards.

These European organisations have members from both the EU and EFTA. In the EU the standards are legally binding as community law. Standards for the EU area are decided by quailified majority between member states in the same way and with the same voting weights as the Council of Ministers decide many laws.

The EU also incorporate many other international standards, e.g. from the United Nations specialised organisation Codex Alimentarius for food standards. Here you can find 4,783 standards.

The EU also cooperate with the Worlds Standards Cooperation, WSC composed by the International Organization for Standardization (ISO), the International Electrotechnical Commission (IEC), and the International Telecommunication Union (ITU).

These standards organisations are all based in Geneva in Switzerland and have representatives from most countries in the world. 

Technical standards are complex. The total number of pages for just Cenelec standards are 156,241, more than the entire EU legislation of 30,000 legal acts which has been calculated to more than 100,000 pages.

See also Number of EU laws, and Acquis Commaunautaire