OpenAI makes GPT-5 the default model in ChatGPT

OpenAI released GPT-5 on 7 August 2025, describing it as a unified model that combined the step-by-step reasoning of the o-series with the faster replies of the GPT series, with a 400,000-token context window. It became the default for free and paid ChatGPT users.

Why it mattered Its rollout problems and moderate benchmark gains fed the year’s argument over whether scaling frontier models still produced improvements in proportion to the cost.