Here Are the Tell

Y Combinator (YC), a well-known startup accelerator that helped launch companies like Reddit, DoorDash and Airbnb, has invested in more than 5,000 startups since 2005. Now YC leaders note that founders seem to be outsourcing writing their applications to AI.

The YC application requires founders to explain how they selected their idea, identify competitors in the space and outline their plans to generate revenue. Some tell-tale signs reveal that many tech-focused founders have recently decided to use AI to write answers to these questions.

One giveaway is the longer responses that AI produces. According to YC partner Tyler Bosmeny, YC applications have increased in length by 60% over the past three years. “I wonder what could explain that…” he wrote on X earlier this week.

Another YC partner, Pete Koomen, spent a week reading applications. He wrote in an X post this week that “back in my day (one year ago) founders didn’t talk like this.” He shared a chart showing that the percentage of applications containing the word “wedge” went from less than 1% in spring 2025 to greater than 20% in summer 2026.

Meanwhile, em dashes, another AI giveaway, started growing in use in 2023 and “really hit their stride in 24,” Koomen said. According to the data he shared, by summer 2025, more than 50% of YC applications used em dashes.

Koomen emphasized that the spacing of those em dashes was important. Em dashes with spaces around them spiked in use in summer 2025, around the same time that the word “wedge” became more popular. These signs of AI use coincided with the launch of Anthropic’s Opus 4 AI model, he said.

YC co-founder Paul Graham wrote in an X post in April 2024 that someone sent him a cold email suggesting “a novel project.” Then he noticed that the email used the word “delve.”

“My point here is not that I dislike ‘delve,’ though I do, but that it’s a sign that text was written by ChatGPT,” Graham wrote in the post, which has been viewed 2.6 million times.

He added a chart created by researcher Philip Shapira, which illustrated that the word “delve” has jumped from nearly zero to nearly 18,000 instances in published papers and articles from 1990 to 2024.

“No one uses it [delve] in spoken English,” Graham wrote. “It’s one of those words like ‘burgeoning’ that people only use when they’re writing and want to sound clever.”

Founders using AI to write applications have recently stayed away from “delve.” Koomen found that the word only spiked in 1.25% of applications in the winter of 2024, before Graham’s post.

Graham said more recently, in an X post in May, that “a lot” of emails from founders now adopt “a hard-hitting journalistic style.”

“I know they’re written by AI, because no founder ever wrote this way before,” he wrote, adding, “It feels like being lied to.”