GPT (OpenAI)

GPT is OpenAI's flagship large language model family — the foundation behind ChatGPT, the most widely used AI assistant with over 300 million weekly active users as of early 2026 (according to OpenAI). The series spans from the lightweight GPT-4o mini for cost-sensitive tasks to the reasoning-focused o3 and o4-mini, and the latest GPT-5 family released in 2026.

What sets GPT apart from competitors like Claude and Gemini is ecosystem breadth. The GPT Store, custom GPTs, Plugins, and a mature API with function calling, structured outputs, and real-time voice capabilities create a developer platform no single competitor matches in scope. Enterprise customers get data processing agreements, SOC 2 compliance, and the option to disable training on their data.

The trade-offs are real. API costs at scale can exceed Claude's pricing significantly — especially for reasoning-heavy o3 workloads. OpenAI's model versioning has historically been inconsistent: GPT-4 Turbo behaved differently enough from GPT-4 that some production workflows broke during the transition. And while OpenAI now offers GDPR options, US-only data residency remains a blocker for regulated European organizations.

For developers building AI-powered products, GPT remains the default starting point — not because it's always the best model, but because its tooling, documentation, and community make iteration fastest. Teams needing stronger coding performance may prefer Claude; those prioritizing open weights should look at Llama 4.