GPT-3.5 Turbo

GPT-3.5 Turbo was released via the OpenAI API in March 2023 and powered the original ChatGPT launched in November 2022. It represented a major improvement over GPT-3 in instruction-following and conversational ability. The model features a 16K token context window (16,385 tokens). Priced at \$0.50/\$1.50 per million tokens (input/output). Largely superseded by GPT-4o mini, which is cheaper and more capable, but remains historically significant as the model behind ChatGPT's viral launch.