I use a local HTML file on all of my computing devices which lists all my frequently-used web sites on a multi-column page, with the individual entries being organized in categories. My new smartphone runs Android 6.0 which, for some reason seems to dislike opening the local HTML file in my favourite web browser, Mozilla Firefox.
The error message “Access to the file was denied” was displayed in lieu of my carefully-crafted menu page. The associated text went on to suggest that “The file… is not readable. It may have been removed, moved, or file permissions may be preventing access. ERR_ACCESS_DENIED”.
It runs out that the latter issue is the problem. The fix is fairly simple. Load Android’s “Settings” menu and navigate to “Apps”. Scroll down to “Firefox”. Tap the Firefox listing to bring up the “App Info” screen. Click on the “Permissions” option, and slide the control for “Storage” to the right to enable file permissions.
Firefox can now open the local HTML file stored, in my case, on the smartphone’s supplementary SDcard.
Requesting Permissions at Run Time