Senior developers use AI for 50% of code vs 13% for juniors

Experienced developers with over 10 years in the field are more than twice as likely to use AI code-generation tools to produce over half of their finished software compared to junior developers, according to new research from Fastly, a cloud services platform. The findings challenge assumptions about AI adoption in programming, revealing that senior developers embrace these tools not out of laziness, but as a strategic response to their broader responsibilities beyond day-to-day coding.

What you should know: A July survey of 791 US developers found stark differences in AI tool usage across experience levels.

• Around 33% of senior developers with more than a decade of experience use AI tools like Copilot, Claude, and Gemini to generate over half their code, compared to just 13% of developers with up to two years of experience.
• Only 1.8% of all respondents said they never use AI code generation tools.
• Over 70% of developers said AI tools made their jobs more enjoyable, while less than 20% found them problematic.

Why this matters: The pattern reflects the evolving role of senior developers rather than a decline in coding skills.

• “When you really zoom out and think about what a senior engineer does, they don’t write code all day,” explained Austin Spires, senior director of developer engagement at Fastly.
• Senior developers can leverage AI to quickly prototype and test ideas, recapturing “that visceral, fun dopamine hit that made coding so fun in the beginning.”

The big picture: Junior developers’ cautious approach to AI tools may actually be beneficial for skill development.

• Spires called it “heartening” that younger coders rely less on AI tools, showing they want to craft code traditionally.
• Newer developers appear to view AI coding tools as helpful supplements rather than replacements for learning fundamental programming skills.

Key performance differences: Experience levels create distinct patterns in how developers interact with AI tools.

• A slight majority of older developers say AI tools help them ship software faster, though they spend more time checking for bugs.
• Fewer than half of junior developers felt AI tools improved their speed.
• Senior developers can more quickly scan code and spot flaws, while younger workers struggle more with software editing.

Environmental awareness gap: The survey revealed significant differences in sustainability consciousness across generations.

• Barely half of younger developers consider the energy costs of running new code, compared to 80% of older programmers.
• Nearly one in ten respondents admitted they don’t know how much energy their software requires.
• “More senior engineers understand the second and third effects of their code in how it relates to users and how it relates to their community,” Spires noted.

What they’re saying: Industry experts see this as a natural evolution in developer practices.

• “There’s not a lot of incentive for AI coding tools to disclose what the carbon footprint of these tools are,” Spires said.
• “I think it’s just a matter of time before junior developers start to understand those ramifications a little bit further.”