All traditional (legacy) add-ons, such as the original Tile Tabs, will not work with Firefox 57 or later versions.

Firefox 57 and later versions will only support add-ons that have been built using the new WebExtensions API's (which are the same as the Chrome extension API's).

Using the WebExtensions API's, it is not possible to display multiple pages simultaneously within the same browser window. This is why Tile Tabs WE has to move each tiled tab into a separate window.

There have been contacts with Mozilla about providing a new WebExtensions interface that would allow a new add-on to be developed that is more similar to the original Tile Tabs. There has been some good progress made with implementation of this interface, but there are some design issues that are blocking further progress.

When this new WebExtensions interface is available, the plan is to develop a new add-on that will work much more like the original Tile Tabs. In fact, there is already a fully developed and working prototype of this new add-on. It is still hoped that this can be completed in time for the release of Firefox 57.

The Tile Tabs popup notification will appear twice more before Firefox 57 is released.