Y Combinator is a startup accelerator that runs four batches of companies each year, each lasting three months. It invests $500,000 per company, structured as $125,000 for 7% on a post-money SAFE plus $375,000 on an uncapped SAFE with a most-favoured-nation clause. It backs companies at pre-seed and seed stage across sectors and geographies, with the programme and weekly meetups run from San Francisco.