Folium
Interactive map visualization library for Python using Leaflet.js — creates interactive HTML maps from Python. Folium features: folium.Map() with OpenStreetMap/Stamen/CartoDB tile layers, Marker/CircleMarker/Popup for points, GeoJSON/TopoJSON overlays, Choropleth for data-driven coloring, PolyLine/Polygon for shapes, MarkerCluster plugin for dense markers, HeatMap plugin, folium.LayerControl for toggle layers, FeatureGroup for organization, save() to HTML, and Jupyter notebook display. Converts Python/pandas data to interactive Leaflet maps without JavaScript knowledge.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
HTML output may contain embedded data including sensitive location info — treat map HTML files as potentially sensitive. Tile API keys (Mapbox) must be in environment variables, not hardcoded in source. Output HTML is self-contained and can be shared/hosted without server.
⚡ Reliability
Best When
Generating interactive HTML maps from Python geospatial data for reports, notebooks, and stakeholder deliverables — Folium produces publication-ready Leaflet maps without JavaScript with excellent choropleth and clustering support.
Avoid When
You need real-time updates, are building a production web app, or have >50K data points without aggregation.
Use Cases
- • Agent location visualization — import folium; m = folium.Map(location=[37.7749, -122.4194], zoom_start=12); for _, row in df.iterrows(): folium.Marker([row.lat, row.lng], popup=row.name, tooltip=row.address).add_to(m); m.save('agent_map.html') — interactive point map from pandas DataFrame; agent analytics generates deliverable map HTML for stakeholders
- • Agent choropleth data map — m = folium.Map(location=[38, -97], zoom_start=4); folium.Choropleth(geo_data=us_states_geojson, data=df, columns=['state', 'value'], key_on='feature.id', fill_color='YlOrRd', legend_name='Agent Coverage').add_to(m) — state-level data coloring on US map; agent analytics visualizes geographic distribution of metrics
- • Agent route visualization — m = folium.Map(location=[center_lat, center_lng], zoom_start=10); folium.PolyLine([[lat1,lng1], [lat2,lng2], [lat3,lng3]], color='blue', weight=3).add_to(m); folium.Marker([lat1,lng1], icon=folium.Icon(color='green', icon='play')).add_to(m) — draw delivery route on map; agent logistics visualizer shows optimized route as interactive polyline
- • Agent cluster map for dense data — from folium.plugins import MarkerCluster; mc = MarkerCluster().add_to(m); [folium.Marker([r.lat, r.lng]).add_to(mc) for _, r in events_df.iterrows()] — MarkerCluster handles 10K+ markers without browser slowdown; agent event monitoring map clusters nearby incidents for legibility at country zoom level
- • Agent heatmap generation — from folium.plugins import HeatMap; HeatMap(data=[[lat, lng, weight] for lat, lng, weight in zip(lats, lngs, weights)], radius=15).add_to(m) — density heatmap of agent activity; agent coverage visualization shows geographic intensity of events as smooth heat overlay
Not For
- • Real-time streaming maps — Folium generates static HTML; for real-time updates use Plotly Dash with Mapbox or deck.gl
- • Production web app maps — Folium outputs standalone HTML; for embedded web app maps use Leaflet.js or Mapbox GL JS directly
- • Large datasets (>10K markers) without clustering — use MarkerCluster plugin or aggregate to heatmap; individual markers >10K make browser unresponsive
Interface
Authentication
No auth for OpenStreetMap tiles. Commercial tiles (Mapbox) require token passed to folium.Map(tiles='mapbox', API_key='token').
Pricing
Folium is MIT licensed. Free with OpenStreetMap tiles. Commercial tile providers cost separately.
Agent Metadata
Known Gotchas
- ⚠ Choropleth key_on must match GeoJSON property exactly — folium.Choropleth(key_on='feature.properties.STATE_ABBR') must match exact key path in GeoJSON; agent code with key_on='feature.id' when GeoJSON uses feature.properties creates blank choropleth with no error; inspect GeoJSON structure first: json.loads(geo_data)['features'][0]
- ⚠ save() produces HTML requiring internet for tiles — m.save('map.html') creates HTML that loads OpenStreetMap tiles from internet; offline environments show blank map background; agent reports for air-gapped environments must use offline tile server or generate static PNG via Selenium/playwright screenshot
- ⚠ Large popup HTML causes browser issues — folium.Popup(html='<table>...long table...</table>') with 100+ row tables causes browser to freeze when clicked; agent popups must be concise or use lazy-loading iframes; limit popup content to 10-20 key fields
- ⚠ Marker coordinates are [lat, lng] not [lng, lat] — folium.Marker([latitude, longitude]) matches Leaflet (y,x) convention; agent code with GeoJSON coordinates (which are [lng, lat] / x,y) must swap: folium.Marker([coords[1], coords[0]]); most common mistake causes markers to appear in wrong hemisphere
- ⚠ CircleMarker radius is in pixels not meters — folium.CircleMarker(radius=10) is 10 pixels screen-space regardless of zoom; for geographic radius use folium.Circle(radius=1000) which is 1000 meters; agent code showing real-world buffer zones must use Circle not CircleMarker
- ⚠ Plugins must be imported separately — from folium.plugins import MarkerCluster, HeatMap, TimestampedGeoJson; they are not in main folium namespace; agent code doing folium.MarkerCluster() raises AttributeError; always import plugins explicitly from folium.plugins
Alternatives
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Scores are editorial opinions as of 2026-03-06.