There are several available versions of the Primer3 web interface: Primer3Web and Primer3Plus

Primer3Web

Primer3Web is the original web-interface to Primer3. Primer3Web was developed by Steve Rozen and Helen Skaletsky. Primer3Web is maintained by Triinu Koressaar and Maido Remm.

Primer3Web at primer3.ut.ee

Primer3Plus

Primer3Plus is an updated, task-oriented web-interface to Primer3. Primer3Plus is developed and maintained by Andreas Untergasser.

Primer3Plus at www.primer3plus.com