Creating Streamlit themes

Build professional, brand-aligned themes using .streamlit/config.toml. This skill covers design principles and complete configuration for polished, cohesive themes.

Theme file setup

Theme options go in Streamlit's config.toml under the [theme] section:

Theme inheritance

Start from a built-in theme or external file:

[theme]
base = "light"                         # or "dark"
# base = "./my-base-theme.toml"        # Local file
# base = "https://example.com/theme.toml"  # Remote URL

When using base, you only need to override the values you want to change. Theme files referenced via base can only contain a single [theme] section, [theme.light] and [theme.dark] variants are not supported in external theme files.

Color configuration

Theme colors

[theme]
primaryColor = "#0969da"           # Buttons, links, active elements
backgroundColor = "#ffffff"        # Main content background
secondaryBackgroundColor = "#f6f8fa"  # Widget backgrounds, code blocks
textColor = "#1F2328"              # Body text

# Optional refinements
linkColor = "#0969da"              # Markdown links (defaults to primaryColor)
codeTextColor = "#1F2328"          # Inline code text
codeBackgroundColor = "#f6f8fa"    # Code block background
borderColor = "#d0d7de"            # Widget borders

Design principle: Choose a primaryColor dark enough to contrast with white text. Streamlit renders the text of primary buttons white against the primary color.

Color palette

Define semantic colors for status indicators, markdown text coloring, and sparklines:

[theme]
redColor = "#cf222e"
orangeColor = "#bf8700"
yellowColor = "#dbab09"
greenColor = "#1a7f37"
blueColor = "#0969da"
violetColor = "#8250df"
grayColor = "#57606a"

Each color supports background and text variants (auto-derived if not set):