Streamlit layout

How you structure your app affects usability more than you think.

Sidebar: navigation + global filters only

The sidebar should only contain navigation and app-level filters. Main content goes in the main area.

# GOOD
with st.sidebar:
    date_range = st.date_input("Date range")
    region = st.selectbox("Region", ["All", "US", "EU", "APAC"])
    st.caption("App v1.2.3")

# BAD: Too much content in sidebar
with st.sidebar:
    st.title("Dashboard")
    st.dataframe(df)  # Don't put main content here
    st.bar_chart(data)

What goes in sidebar:

Global filters (date range, user selection, region)
App info (version, feedback link)

What stays out:

Main content, charts, tables, results

Columns: max 4, set alignment

Don't use too many columns—they get cramped.

# GOOD
col1, col2 = st.columns(2)

# Custom widths (ratios)
col1, col2 = st.columns([2, 1])  # 2:1 ratio

# OK with alignment
cols = st.columns(4, vertical_alignment="center")

# BAD: Too many, cramped
col1, col2, col3, col4, col5, col6 = st.columns(6)

Horizontal containers for button groups

Use st.container(horizontal=True) instead of columns for button groups:

with st.container(horizontal=True):
    st.button("Cancel")
    st.button("Save")
    st.button("Submit")

Aligning elements

Use horizontal_alignment on containers to position elements:

# Center elements
with st.container(horizontal_alignment="center"):
    st.image("logo.png", width=200)
    st.title("Welcome")

# Right-align elements
with st.container(horizontal_alignment="right"):
    st.button("Settings", icon=":material/settings:")

# Distribute evenly (great for button groups)
with st.container(horizontal=True, horizontal_alignment="distribute"):
    st.button("Cancel")
    st.button("Save")
    st.button("Submit")

Options: "left" (default), "center", "right", "distribute"

Bordered containers

Use border=True on containers for visual grouping. See building-streamlit-dashboards for dashboard-specific patterns like KPI cards.

with st.container(border=True):
    st.subheader("Section title")
    st.write("Grouped content here")

Tabs

Organize content into switchable views:

tab1, tab2 = st.tabs(["Chart", "Data"])

with tab1:
    st.line_chart(data)
with tab2:
    st.dataframe(df)

Expander

Collapsible sections for secondary content:

with st.expander("See details"):
    st.write("Hidden content here")
    st.code("print('hello')")

Empty and placeholders

st.empty() creates a single-element placeholder that can be updated or cleared:

placeholder = st.empty()

# Update the placeholder
placeholder.text("Loading...")
result = load_data()
placeholder.dataframe(result)

# Clear it
placeholder.empty()

Popover

Click to reveal content:

with st.popover("Settings"):
    st.checkbox("Dark mode")
    st.slider("Font size", 10, 24)

Dialogs for focused interactions

Use @st.dialog for UI that doesn't need to be always visible:

@st.dialog("Confirm deletion")
def confirm_delete(item_name):
    st.write(f"Are you sure you want to delete **{item_name}**?")
    if st.button("Delete", type="primary"):
        delete_item(item_name)
        st.rerun()

if st.button("Delete item"):
    confirm_delete("My Document")

Key points:

Dialogs rerun independently from the main script
Use st.session_state to pass widget values from the dialog to the main app
Call st.rerun() to close dialog and refresh main app
Use dismissible=False for forced actions
st.sidebar is not supported inside dialogs

When to use dialogs:

Confirmation prompts
Settings panels
Forms that don't need to be always visible

Spacing

Control spacing between elements with gap on containers:

# Remove spacing for tight list-like UIs
with st.container(gap=None, border=True):
    for item in items:
        st.checkbox(item.text)

# Explicit gap sizes
with st.container(gap="small"):
    ...

Add vertical space with st.space:

st.space("small")   # Small gap
st.space("medium")  # Medium gap
st.space("large")   # Large gap
st.space(50)        # Custom pixels

Width and height

Control element sizing:

# Stretch to fill available space (equal height columns)
cols = st.columns(2)
with cols[0].container(border=True, height="stretch"):
    st.line_chart(data)
with cols[1].container(border=True, height="stretch"):
    st.dataframe(df)

# Shrink to content size
st.container(width="content")

# Fixed pixel sizes
st.container(height=300)

using-streamlit-layouts