About OpenAI
OpenAI is an AI research organization founded in 2015 by Sam Altman, Greg Brockman, Ilya Sutskever, and others, with early backing from Elon Musk. Originally a non-profit, OpenAI transitioned to a capped-profit model in 2019. The company is responsible for the GPT family of language models that popularized AI assistants worldwide through ChatGPT (launched November 2022).
OpenAI operates two distinct model lines: the GPT series (general-purpose) and the o-series (reasoning-specialized). The o-series models (o1, o3, o4-mini) use extended “thinking” time to solve complex math and reasoning problems, achieving dramatically higher scores on competition-level benchmarks. The o3 model leads with 88.9% on AIME 2024 and 83.3% on GPQA Diamond.
GPT & o-Series Timeline
The evolution of OpenAI’s model families from GPT-4 through GPT-5 and the o-series reasoning models. All scores from official OpenAI announcements.
GPT-5
OpenAI’s latest general-purpose model. Advances in knowledge breadth, multimodal understanding, and instruction following.
o3
The full o3 reasoning model. Achieves 88.9% on AIME 2024 and 83.3% on GPQA Diamond, setting new records for AI mathematical and scientific reasoning. Uses extended chain-of-thought during inference. Source: OpenAI announcement.
o4-mini
Cost-efficient reasoning model with strong performance. Achieves 81.4% on GPQA Diamond and 92.7% on AIME 2025. Source: OpenAI announcement.
GPT-4.1
An updated GPT-4 class model with improved knowledge and reasoning capabilities. Source: OpenAI announcement.
GPT-4.5
Incremental update bridging GPT-4o and GPT-5. Improved knowledge depth, stronger multilingual performance, and better calibration.
o3-mini
Cost-efficient reasoning model. Delivers strong math and coding performance at a fraction of the cost of full o3, making reasoning accessible for more applications. Source: OpenAI announcement.
o1
Full release of the o1 reasoning model. Achieves 92.3% on MMLU, 78.0% on GPQA Diamond, and 83.3% on AIME 2024—dramatically improved over o1-preview. Source: OpenAI blog.
o1-preview
Introduced the revolutionary “thinking” paradigm. First model to use extended reasoning chains during inference, achieving 73.3% on GPQA Diamond and 44% on AIME 2024. Source: OpenAI blog.
GPT-4o
The “omni” model. Natively multimodal with text, image, and audio understanding. Achieves 87.2% on MMLU and 49.9% on GPQA Diamond. Cross-referenced from DeepSeek-R1 paper.
GPT-4
The model that defined the frontier. GPT-4 was the first large language model to pass the bar exam and demonstrated broadly superhuman text understanding. Launched the “AI race” among major tech companies.
Benchmark Performance
GPT-5 scores across verified benchmark categories.
Key Strengths
The o3 model achieves 88.9% on AIME 2024. The o-series’ extended thinking approach has redefined what’s possible in competition-level math.
o3 achieves 83.3% on GPQA Diamond, o1 reaches 78.0%—both demonstrating strong expert-level scientific reasoning through chain-of-thought inference.
With 92.3% on MMLU, the o1 model demonstrates one of the widest knowledge bases among frontier models, covering STEM, humanities, and professional domains.
Two-Track Strategy: GPT vs o-Series
OpenAI uniquely maintains two parallel model lines. The GPT series (GPT-4o, GPT-4.1, GPT-5) prioritizes balanced, fast performance for everyday tasks. The o-series (o1, o3, o4-mini) sacrifices speed for dramatically better performance on hard reasoning problems. For competition math, o3 (88.9% AIME 2024) far exceeds GPT-4o (9.3% AIME), but at significantly higher cost and latency.
Benchmark scores are snapshots at time of release and may not reflect your specific use case.
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