More than half of code shipped by senior developers could be AI generated, according to survey findings.
AI-generated code accounted for more than half of shipped code among nearly one-third of senior developers who participated in a recent survey by cloud platform provider Fastly.
The company’s July 2025 survey of 791 professional developers found that 32% of senior developers (those with 10 or more years of experience) said more than half of their shipped code was AI-generated. Among junior developers, just 13% said the same. Fastly’s findings suggest that more experienced engineers not only are using AI more aggressively but also may trust it more in production environments. This is surprising given growing concerns about vibe coding introducing vulnerabilities into code, said Fastly.
Nearly one in three developers (28%) said they fixed or edited AI-generated code frequently enough to offset most of the time savings. Only 14% said they rarely needed to make changes. And yet, more than half of developers said they felt they worked faster with AI tools like Copilot, Gemini, or Claude. “AI will bench-test code and find errors much faster than a human, repairing them seamlessly. This has been the case many times,” one senior developer wrote. A junior respondent cited trade-offs: “It’s always hard when AI assumes what I’m doing and that’s not the case, so I have to go back and redo it myself.”
Senior developers also were more likely to say they invested time in fixing AI-generated code. Just under 30% of senior developers reported editing output enough to offset most of the time savings, compared to 17% of junior developers. But 59% of senior developers said AI tools helped them ship code faster overall, compared to 49% of junior developers. Also, slightly more than half of junior developers reported that AI made them moderately faster, whereas only 39% of senior developers said the same. Still, senior developers were twice as likely as junior developers to report significant speed gains. Fastly said one reason for this gap could be that senior developers are better equipped to catch and correct AI mistakes.
Nearly 80% of all respondents said AI tools made coding more enjoyable. Some developers might appreciate skipping grunt work, while others enjoy the dopamine rush of code on demand, according to Fastly. Survey results were released August 27. The survey was conducted from July 10 to July 14, 2025, with 791 professional developers responding.
