An accelerator is a fixed-term, cohort-based program that invests a small amount in early-stage startups in exchange for equity, then runs an intensive mentorship and curriculum program ending in a public demo day. Y Combinator, founded in 2005, set the modern template; Techstars, 500 Global, Antler, and hundreds of regional and industry-vertical programs followed.
The structure is consistent across programs. A startup applies, interviews, and (if accepted) joins a cohort of 10 to 250 companies. The program runs 10 to 16 weeks. The investment is usually structured as a with a single set of standard terms across the cohort, plus a smaller cash stipend in exchange for common shares. Founders meet with mentors, attend office hours, sit through founder talks, and prepare a pitch for demo day, where investors decide who to follow on with seed checks.
The cash check is the smallest part of the value. As of 2026, top programs invest between $125K and $500K. Meaningful for a pre-product team, but a fraction of what a seed round raises afterward. The real assets are the network of alumni, the mentor pool, the brand-name on a deck, and the demo-day funnel that compresses what would otherwise be six months of investor outreach into two weeks.
Equity. Most programs take between 5% and 10% of the company on standard terms. Y Combinator's current deal is $125K for 7% common plus $375K of uncapped MFN SAFE. Techstars is $20K for 5% common plus $200K of uncapped MFN SAFE. That equity is permanent. Every percentage point given up early is gone.
When the program's network meaningfully shortens your seed-round timeline, when you don't yet have enough warm investor introductions to run a process on your own, or when the mentorship matches the specific gaps in your team. Less so when you're already raising on good terms, when the cohort is mismatched to your sector, or when the equity ask outweighs the upside of bootstrapping another six months.