Issued by Intertek Group PLC, the ETL mark (previously a mark issued by Electrical Testing Laboratories, hence the ETL name) is an alternative to the UL and CSA marks. Intertek tests products against the applicable UL standards before deciding whether to issue the ETL mark. Similarly, the Canadian Standards Association is a nonprofit association that tests products against the UL standards to ensure public safety.

The CSA, UL, and Intertek Group testing facilities are all Nationally Recognized Testing Laboratories (NRTLs), a United States Occupational Safety and Health Administration (OSHA) designation given to testing facilities that provide product-safety testing and certification services to manufacturers. If a product (not just one or more components) has been fully tested and has one of these marks that is applicable to the entire product, it means that the product and all of its components have been tested as they are used in connection with one another and have been deemed to meet the applicable safety standard for that particular product.