Streamlit

Streamlit is an open-source Python framework that turns data scripts into shareable web apps: write Python top-to-bottom, and every widget interaction reruns the script. There is no frontend code, no callbacks to wire up — st.slider, st.dataframe, and st.chat_input give you interactive apps in minutes, which made it the default UI layer for data science and LLM prototypes.

Snowflake acquired Streamlit in 2022 and made it a first-class citizen of the data cloud: Streamlit in Snowflake (SiS) runs apps natively inside Snowflake with governed data access, and Streamlit became the standard way to build Cortex AI chat interfaces against enterprise data. The ecosystem includes thousands of custom components and a free Community Cloud for public apps.

Limitations: the top-to-bottom rerun model gets awkward for complex stateful apps; Community Cloud is free but limited (apps sleep, one private app); the commercial path is Streamlit in Snowflake, which ties you to the Snowflake platform; and highly custom designs hit the limits of the component model.

pip install streamlit; write app.py and run streamlit run app.py. Deploy free on Streamlit Community Cloud or natively in Snowflake.