Scale announced the close of a series D funding round in which it raised $155 million at a $3.5 billion post-money valuation.
The funding round — which more than tripled Scale's previous valuation — was led by investment firm Tiger Global Management.
Founded in 2016, Scale set out to automate data labeling, one of the most labor-intensive stages of AI development. Scale developed internal machine learning programs for data labeling, though it also uses human contractors to perform manual reviews in some cases. General Motors, Toyota, Airbnb, OpenAI, Otto Motors and the U.S. military have all contracted data-labeling services from Scale.