DeepSeek

DeepSeek offers a free web and mobile chat app built on its V3 and R1 model families, which have drawn attention for matching much of the reasoning, math, and coding performance of premium Western models at no cost to end users. A standout feature is the "DeepThink" mode, which shows the model's step-by-step reasoning before giving a final answer — useful for verifying how it arrived at a conclusion. The underlying model weights are also released openly, so developers can self-host on their own infrastructure for full data control. The trade-offs are that the official app routes data through servers based in China, which raises data-residency questions for some users and organizations, the web app can be slow or unavailable during peak demand, and the interface is noticeably more basic than ChatGPT or Claude.