Explorer fails to load inside iframe in Microsoft Edge (Tracking Prevention blocks storage)

Description

reported by @mortymort85

Summary

When explore.overturemaps.org is embedded as an iframe (e.g. the explorer embed on the overturemaps.org site), the map fails to initialize in Microsoft Edge with the default (strict?) Tracking Prevention enabled. Instead of the map, we see an error placeholder. The identical embed works in Chrome and Safari.

Console output (Edge)

Tracking Prevention blocked access to storage for
https://cdnjs.cloudflare.com/ajax/libs/iframe-resizer/4.3.9/iframeResizer.min.js

"Tracking Prevention blocked access to storage" --> Edge's Tracking Prevention partitions/denies storage to cross-origin embedded content it classifies as a tracker.

Root cause (suspected)

Overture Explorer requires access to browser storage to initialize (e.g. state, cached tiles, tokens). When Edge denies storage to the embed, we get an error. This is expected behavior for cross-origin iframes under Edge Tracking Prevention and cannot be overridden by the embedding page.

Steps to reproduce

See below

Suggested improvement

Consider having Overture Explorer degrade gracefully when partitioned/blocked storage is detected — for example, catch the storage-access failure and fall back to an in-memory or read-only mode so embedded maps still render, rather than showing a hard error. Detecting the blocked-storage condition and surfacing a short, actionable message (or a link to open in a new tab) would also help embedders.

Workaround for affected users

In Edge: allow the site under Settings → "Privacy, search, and services" → Tracking prevention → Exceptions → add overturemaps.org, or toggle Tracking Prevention off for the site via the address-bar icon, then reload.

What browser are you seeing the problem on? What version are you running?

Edge

The OS you're using

Windows

Steps to reproduce

1. In Microsoft Edge with default (Balanced) Tracking Prevention, open a page that embeds explore.overturemaps.org in an iframe.
2. Observe the map fails to load and shows the error placeholder.
3. Open DevTools → Console; observe Tracking Prevention blocked access to storage warnings.
4. In Chrome, load the same page — the map renders normally.
5. In Edge, add overturemaps.org as a Tracking Prevention exception (or disable it for the site) and reload — the map now renders.

The browser URL at the time you encountered the bug

https://overturemaps.org

Start by reproducing the explore.overturemaps.org iframe in Microsoft Edge with default Tracking Prevention and inspect the DevTools console for the storage warning. Trace the Explorer initialization path that fails when embedded storage is blocked; done means the map renders in the iframe or shows an actionable fallback instead of the error placeholder.