YouTube Error 153 and Leaflet maps error Access Blocked 403r

 Users of the Memory Keeper are likely to expericence these two errors:

1. Map error: Access blocked 403r

2. YouTube Error 153:

OpenStreetMap (OSM) tile layer server has a new security policy (enforced strictly as of early 2026) blocks any request that doesn't identify where it's coming from. OpenStreetMap's policy specifically mentions that file:// URLs are problematic and they recommend using a local server environment to ensure identifying information is sent correctly. When you open a local HTML file, your browser sees there is no "website" (domain) associated with it. To protect your local file paths (which could contain your username or sensitive folder names), the browser sends a blank or "null" referrer. The Result: OSM gives you a 403r, and YouTube often gives a 403 Forbidden, a generic "Video Unavailable" error, or an "Error 153".

For example, when you view YouTube videos and OSM maps in the MK online help documentation, they properly work without these errors. This is because the MK solution is hosted by a web server.

Therefore, the only 100% reliable way to satisfy both OSM and YouTube while working locally is to run a small local web server, like Node.js. However, this is not ideal for most MK and TW users. I too personally like to use the local file. So, for the rest of us here is what I do:

1. YouTube videos: I accept the Error 153 and click on the link "Watch video on YouTube".

2. OSM has been the default map type since MK was released. Starting in MK 1.0.05 this will not be case. OSM France will be default tile set. In all versions of MK the user can change the default tile. Navigate to the Control Panel-->Info (tab)-->Memory Keeper (tab)-->Settings (tab), and under General Settings scroll down to the setting "Default leaflet map"... and change the drop down setting to "OSM France" or any option you prefer.

Each Leaflet map (not Google Maps) has a menu button in the upper right of the map. Click to open the menu. From this list you can see which map is selected. Change the selection from OpenStreetMap to another map.

However, this is a one-time change and does not change the default setting. Therefore, change the default setting as mentioned above.

TIP: When it makes sense to do so, use the "mapit" tag for place tidders. This will use Google Maps, To properly use this tag, you need to populate the Address fields including Address Line 1, Address Line 2, City, Dependent Locality, City/Town/Village, State/Province/Region, and Country fields. When mapit is used it will use this field to properly locate the map. Note: When defining a historical place/territory it may not exist on a modern Google Map. So, you populate these fields with the modern information, so Google Maps can map the appropriate place.