Nico Mylist Add Contener is a free Chrome add-on developed by naari3. It falls under the category of Browsers and is classified as an Add-ons & Tools subcategory.

This add-on allows users to add a Mylist function to the NicoNico video player. With Nico Mylist Add Contener, users can add a button to the player that enables them to register videos to their Mylist without having to switch to a different tab or window. This feature eliminates the need for users to navigate away from the video they are watching, making the Mylist registration process more efficient and convenient.

It is worth noting that NicoNico has recently implemented the functionality that this extension offers, rendering its use unnecessary. Therefore, it is recommended to use the built-in Mylist functionality provided by NicoNico instead of this add-on.