What is Y Combinator's acceptance rate? How fierce is the competition?

Let's put it this way: getting into YC is much harder than getting into Harvard or Stanford.

The commonly cited acceptance rate fluctuates between 1.5% and 3%. However, this is just a rough figure, and it varies with each batch.

To give you a more intuitive sense:

Imagine that for each batch (YC has two per year), thousands, perhaps even ten or twenty thousand, of startup teams from all over the world submit applications. Yet, only about two to three hundred companies ultimately make it in.

So, it's not just a simple "one in a hundred" scenario; it's truly "one in a hundred" or "two in a hundred" in terms of selection.

Why is the competition so fierce?

1. Extremely High Caliber Applicants: You're not competing with ordinary people. Many are PhDs from prestigious universities, top engineers from major companies, or "serial entrepreneurs" who have already had successful ventures. They all come with brilliant ideas and already-built product prototypes.
2. Global Competition: Your competitors come from Silicon Valley, Europe, India, China... essentially the smartest and most ambitious people worldwide.
3. YC's Brand Effect: Being selected by YC is a huge endorsement in itself, akin to stamping your project with a "seal of excellence." This makes subsequent fundraising much easier. That's why everyone is scrambling to get in.

In short: Think of it as the "Olympics" or "World Cup" finals of the startup world. Those who get in are top-tier players. While it's incredibly difficult, that's precisely why the YC halo is so valuable.