It was founded by Claire Novorol, a British pediatrician, Martin Hirsch and Daniel Nathrath. Nathrath is a graduate of the University of Houston Law Center. The company has raised $69.3 million since it was founded in 2011.
The app started out as a platform service for doctors and was adapted in 2016 to focus on the bits patients could understand[clarification needed]. The app takes reported symptoms, matches them with symptoms of patients of similar age and gender, and reports the statistical likelihood that the patient has a certain condition. The detailed report, compiled by Ada, can be sent to a doctor as a PDF.
The app is available in English, German, Spanish and Portuguese. In September 2018 it had been downloaded about five million times. It is free of charge and has the highest consumer ranks among similar apps. It is to be made available in Swahili and in Romanian thanks to funding from the Bill & Melinda Gates Foundation and Fondation Botnar.
Ada has been compared to WebMD, Babylon's GP at Hand app and Your.MD. In October 2017, when three apps were tested with symptoms from asthma, shingles, alcohol-related liver disease, and urinary tract infection, Ada performed very well; it asked about the most important symptoms and provided the best diagnoses. It produced diagrams showing which of the symptoms for each disease were present and the strength of the link, and a diagram of the percentage of people likely to have that diagnosis.
In October 2019 a German IT security professional claimed that the Ada app was sending sensitive user-data (f.e. symptoms, IPs, Android ad IDs etc) to the Amplitude product analytics service (api.amplitude.com), and some German users' insurance provider to their Facebook Analytics account.  
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