December 2025 Estimates
Estimated market state one month before our January 2026 survey
Estimation Methodology
How We Derived These Estimates
These figures are backward projections based on our January 2026 survey data and contextual signals from developer communities. They are not based on a December 2025 survey.
- 64.8% of January respondents reported "significantly increased" usage in the prior 6 months
- Claude Code's rapid rise coincided with the Claude 3.5 Sonnet improvements (late 2025)
- GitHub Copilot was the established market leader throughout most of 2025
- Agentic tools (Claude Code, Cursor) began displacing autocomplete-style tools in Q4 2025
We present these estimates with appropriate epistemic humility. The AI coding tool landscape evolved rapidly between December 2025 and January 2026. Claude Code's meteoric rise, in particular, accelerated in the final weeks of 2025 as word-of-mouth spread through developer communities. Our estimates attempt to capture the state just before this inflection point.
Estimated Market State
We estimate December 2025 represented the final months of GitHub Copilot's market leadership. While AI-assisted coding was already widespread, the market was more fragmented. Claude Code was gaining momentum but had not yet achieved the dominance we observe in January 2026. The "heavy user" segment was smaller, and a meaningful population of developers had not yet integrated AI into their primary workflow.
The transition was driven by a capability gap. In late 2025, developers began recognizing that context-aware, agentic tools offered fundamentally different value than autocomplete-style suggestions. This realization—combined with Claude's model improvements—created conditions for the rapid market restructuring we documented one month later.
Estimated AI Coding Tool Index
We estimate GitHub Copilot held the #1 position in December 2025. As the incumbent with enterprise distribution through GitHub and VS Code integration, Copilot had accumulated a large user base over 2024-2025. However, discussions on Hacker News, Reddit r/programming, and developer Twitter in late 2025 showed growing dissatisfaction with autocomplete-only assistance.
Claude Code was the fastest-growing tool but had not yet reached critical mass. We estimate its market share was roughly half of what we measured in January 2026. Cursor had established itself as the preferred IDE for AI-first development, while ChatGPT/Claude chat remained popular for ad-hoc queries but was being replaced by integrated tools for sustained coding work.
- 1 GitHub Copilot ~35% → 21% (Jan)
- 2 Claude Code ~32% → 69% (Jan)
- 3 ChatGPT / Claude chat ~30% → 25% (Jan)
- 4 Cursor ~22% → 27% (Jan)
- 5 Codex CLI ~10% → 16% (Jan)
- 6 Antigravity ~5% → 12% (Jan)
Estimated AI Adoption by Experience
We estimate the "heavy user" cohort was materially smaller in December 2025. Based on the 65% of respondents who reported "significantly increased" usage over 6 months, we back-calculate that heavy usage (76%+) was approximately 13 percentage points lower across experience levels.
Notably, we believe the experience-level uniformity already existed. The pattern of veterans adopting at similar rates to juniors was likely established by late 2025, driven by improvements in AI model quality that made the tools genuinely useful for complex, production-grade work—the kind experienced developers actually do.
| Experience | 76-100% | 51-75% | 26-50% | 1-25% | 0% |
|---|---|---|---|---|---|
| <2 years | ~55% | ~10% | ~15% | ~12% | ~8% |
| 2-5 years | ~42% | ~22% | ~18% | ~12% | ~6% |
| 6-10 years | ~38% | ~20% | ~18% | ~16% | ~8% |
| 11-20 years | ~40% | ~18% | ~16% | ~18% | ~8% |
| 20+ years | ~44% | ~18% | ~14% | ~16% | ~8% |
Estimated Productivity Perception
We estimate productivity perception was already strongly positive in December 2025, but not yet at the levels we measured in January. The approximately 8 percentage point increase (85% → 93%) over one month aligns with two factors: first, more developers reaching proficiency with AI tools during the holiday period when they had time to experiment; second, the release of improved models that reduced frustrating failure modes.
The veterans' perfect score (100% reporting gains) likely emerged in the December-January transition. In December, we estimate perhaps 90-92% of 20+ year veterans reported gains—still remarkably high, but with a small skeptical minority that was won over by year-end improvements.
Estimated vs. measured productivity gains by experience level
What Changed: December → January
Several factors converged to accelerate the transition we documented. Understanding these helps contextualize both the December estimates and the January measurements.
| Metric | Dec 2025 (Est.) | Jan 2026 (Measured) | Change |
|---|---|---|---|
| Market leader | GitHub Copilot | Claude Code | Disrupted |
| Claude Code share | ~32% | 68.7% | +37 pts |
| Heavy users (76%+) | ~42% | ~55% | +13 pts |
| Report productivity gains | ~85% | 93% | +8 pts |
| Zero AI usage | ~7% | ~1% | -6 pts |
| Dominant paradigm | Autocomplete | Agentic | Shifted |
Contextual Signals — Late 2025
Our estimates are informed by community signals from late 2025. While not systematic measurements, these provide context for the rapid changes we observed:
Copilot feels like autocomplete. Claude Code feels like pair programming with a senior engineer who's read the entire codebase.
— Sentiment from Hacker News threads, Nov-Dec 2025
I switched from Copilot to Claude Code over the Thanksgiving break and I'm not going back. The difference is night and day.
— Common theme in Reddit r/programming, Dec 2025
The agentic tools finally work well enough that I trust them with real code. Six months ago I wouldn't have said that.
— Developer community sentiment, late 2025
Limitations & Caveats
These December 2025 figures are estimates, not measurements. We present them to provide context for the January 2026 survey results and to illustrate the velocity of change in this market. Readers should treat specific numbers as directionally indicative rather than precise.
Key uncertainties include:
- The exact timing of Claude Code's adoption inflection point
- Whether our January sample's characteristics (AI-curious, early adopter) were consistent in December
- Regional and company-size variations we cannot model from available data
- The impact of holiday breaks on tool experimentation and adoption
Nevertheless, the directional story is robust: December 2025 was the end of an era where autocomplete-style tools dominated. January 2026 marks the beginning of the agentic tool era.