The Difference Between MFi and USB-IF Certification

MFi

This program was created by Apple and only applies to their products. To be certified, each product has to meet specific criteria, guaranteeing a baseline level of performance and reliability. Apple didn't invent USB, so those cables cannot be MFi certified---unless it's a Lightning to USB/USB-C cable.

You can learn more about identifying counterfeit Apple accessories here.

USB-IF

The Universal Serial Bus-Implementers Forum (USB-IF) establishes and maintains USB standards. It only applies to USB cables. Like MFi, they have to meet particular specifications.

Summary

MFi and USB-IF are certifications from different groups. It's good to look for one or the other when shopping for a new accessory, so you know you're getting a quality product.