Survey: a third of senior developers say over half their code is AI-generated

Summary

Fastly’s July 2025 survey of 791 developers found a notable difference in how much AI-generated code is making it into production. About a third of senior developers (10+ years of experience) say over half their shipped code is AI-generated — nearly two and a half times the rate reported by junior developers (0–2 years of experience), at 13%.“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 said. A junior respondent noted the 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 were also more likely to say they invest time fixing AI-generated code. Just under 30% of seniors reported editing AI output enough to offset most of the time savings, compared to 17% of juniors. Even so, 59% of seniors say AI tools help them ship faster overall, compared to 49% of juniors.Senior Developers Are More Optimistic About AI Saving TimeJust over 50% of junior developers say AI makes them moderately faster. By contrast, only 39% of more senior developers say the same. But senior devs are more likely to report significant speed gains: 26% say AI makes them a lot faster, double the 13% of junior devs who agree.One reason for this gap may be that senior developers are simply better equipped to catch and correct AI’s mistakes. They have the experience to recognize when code “looks right” but isn’t. That makes them more confident at using AI tools efficiently, even for high-stakes or business-critical code. By contrast, junior developers may not fully trust their ability to spot errors, which can make them more cautious about relying on AI, or more likely to avoid using it in production at all.That tracks with how much AI-generated code actually makes it into production. Among junior devs, just 13% say over half of their shipped code is AI-generated. By contrast, 32% of senior developers say the sa...