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
.streamlit/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
[theme] section of a
[theme] primaryColor="#F63366" backgroundColor="#FFFFFF" secondaryBackgroundColor="#F0F2F6" textColor="#262730" 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
st.text_input (when focused).
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 plot background color for
st.plotly_chart and as the background color for most other interactive
This option controls the text color for most of your Streamlit app.
Selects the font used in your Streamlit app. Valid values are
"monospace". This option defaults to
"sans serif" if unset
Note that code blocks are always rendered using the monospace font regardless of the font selected here.
An easy way to define custom themes that make small changes to one of the
preset Streamlit themes is to use the
base option. Using
Streamlit Light theme can be recreated as a custom theme by writing the
base option allows you to specify a preset Streamlit theme that your
custom theme inherits from. Any theme config options not defined in your theme
settings have their values set to those of the base theme. Valid values for
For example, the following theme config defines a custom theme nearly identical
to the Streamlit Dark theme, but with a new
[theme] base="dark" primaryColor="purple"
base itself is omitted, it defaults to
"light", so you can define a
custom theme that changes the font of the Streamlit Light theme to serif with
the following config