Theme option reference

In this guide, we provide examples of how Streamlit page elements are affected by the various theme config options. For a more high-level overview of Streamlit themes, see the Themes section of the main concepts documentation.

Streamlit themes are defined using regular config options: a theme can be set via command line flag when starting your app using streamlit run or by defining it in the [theme] section of a config.toml file. For more information on setting config options, please refer to the Streamlit configuration documentation.

The following config options show the default Streamlit Light theme recreated in the [theme] section of a config.toml file.

font="sans serif"

Let’s go through each of these options, providing screenshots to demonstrate what parts of a Streamlit app they affect where needed.


primaryColor defines the accent color most often used throughout a Streamlit app. A few examples of Streamlit widgets that use primaryColor include st.checkbox, st.slider, and st.text_input (when focused).

Primary Color


Any CSS color can be used as the value for primaryColor and the other color options below. This means that theme colors can be specified in hex or with browser-supported color names like “green”, “yellow”, and “chartreuse”. They can even be defined in the RGB and HSL formats!


Defines the background color used in the main content area of your app.


This color is used where a second background color is needed for added contrast. Most notably, it is the sidebar’s background color. It is also used as the border and header color for st.dataframe, the plot background color for st.plotly_chart, and as the background color for most other interactive widgets.

Secondary Background Color


This option controls the text color for most of your Streamlit app.


Selects the font used in your Streamlit app. Valid values are “sans serif”, “serif”, and “monospace”. This option defaults to “sans serif” if unset or invalid.

Note that code blocks are always rendered using the monospace font regardless of the font selected here.