Symcat is an online diagnostic tool that, based on a collection of specified symptoms, presents a list of possible diseases (together with their likelihood), .

The site collects information about the user’s symptoms in a comprehensive way; for example, it displays a list of alternative suggestions when a specified symptom is not recognized; it also prompts the user to specify for how long was the symptom previously present. The list of possible diseases is displayed up-front, but it is fine-tuned as the user fills out more details about what he’s experiencing.

The accuracy of possible diseases based on the specified symptoms is what makes this app great. In March 2012, the site was reviewed in LifeHacker, and overall it received a positive review in the articles where it was mentioned.

Symcat was developed by two medical student entrepreneurs from Johns Hopkins, Craig Monsen and David Do. The webapp is currently free of charge, and anyone can use it anonymously.