How do I share a Folium map with someone who doesn't run Python?

Call `m.save('map.html')` and POST the file to https://commareports.com/api/v1/reports with a Bearer comma_sk_ token. Comma renders it in a sandboxed iframe with scripts enabled, so the recipient gets a real pannable, zoomable Leaflet map at a URL — no Python, no notebook, no install.

Do the tiles and markers load inside Comma?

Yes. Folium loads Leaflet from jsdelivr and cdnjs, both of which are on Comma's script CSP allowlist, and map tiles are images, which are allowed from any HTTPS origin. Popups, marker clusters and layer controls behave as they do locally.

What about a custom tile provider that needs an API key?

It works the same way it does anywhere else — the key is in the tile URL, so anyone with access to the report can read it. Use a domain-restricted or throwaway key for anything you publish, and keep the report private or team-visible.

My map with 50,000 markers is enormous. Any options?

Use MarkerCluster or FastMarkerCluster, which cuts both file size and render time dramatically, or aggregate to a heatmap layer. The HTML cap is 5 MB and raw marker lists blow through it quickly.

Can the map update on a schedule?

Yes. A routine can re-render the map on a cron and PATCH the same report id, so the URL stays put while each run appends a revision.

Share a Folium map

A Folium map is one of the friendliest things Python can produce and one of the least shareable. m.save("map.html") writes a working Leaflet app; then it sits in a working directory, and the person who needs it gets a screenshot of the map at exactly one zoom level — which is to say, none of the map.

Publish it

import folium, requests, os
from folium.plugins import MarkerCluster

m = folium.Map(location=[40.71, -74.01], zoom_start=11)
cluster = MarkerCluster().add_to(m)
for row in sites.itertuples():
    folium.Marker([row.lat, row.lon], popup=row.name).add_to(cluster)

m.save("map.html")

requests.post(
    "https://commareports.com/api/v1/reports",
    headers={"Authorization": f"Bearer {os.environ['COMMA_API_TOKEN']}"},
    json={"title": "Service coverage — NYC", "html": open("map.html").read()},
).raise_for_status()

Folium's generated file pulls Leaflet and its plugins from jsdelivr and cdnjs — both allowlisted for scripts inside report HTML — and tiles are plain image requests, allowed from any HTTPS origin. So the published map pans, zooms, clusters and pops exactly like the local one.

What the URL changes

The reviewer explores instead of squinting. Zoom to their own borough, check their own site.
Comments pin to context. Wrap the map in a short brief — what changed, what decision is pending — and the discussion anchors to that text. See commenting on HTML.
A map per week, one URL. PATCH the same report id and coverage drift becomes a revision history instead of a folder of dated files.

Keep the key quiet

If you use a paid tile provider, the token is embedded in the tile URL — that is true of any static Leaflet export. Publish with a domain-restricted key, and keep the report private or team-visible; see the sharing model. Reports are private by default.

Limits

HTML body: 5 MB. Cluster or aggregate before saving; raw marker arrays are the usual culprit.
Scripts run, sandboxed: allow-scripts, no allow-same-origin.
60 requests/minute per token.

Try it

Comma is free — unlimited reports, unlimited commenters, unlimited revision history.

Publish a map →