<big>'''Add-ons Guide for Thunderbird 57 and beyond'''</big>
'''Legacy add-ons''': Despite Mozilla core interface removals, Thunderbird 57-60 and beyond and Seamonkey will '''<u>still support</u> legacy add-ons <u>if</u> appropriate modifications are done to the add-on to adapt to the changed interfaces'''. Core interface changes and removals have come because Mozilla core have disabled "legacy" add-ons (add-ons which are not based purely on WebExtensions) in Firefox 57. Because legacy add-ons are not supported from mozilla57 any more, many interfaces have been removed from Mozilla core.
Despite the interface removals, Thunderbird 57-60 and beyond and Seamonkey will '''<u>still WebExtension''': WebExtension does not exist yet in Thunderbird. Thunderbird will be adding WebExtension support</u> these as ({{bug|1396172}}) while maintaining "legacy " add-ons <u>if</u> the appropriate modifications are done to the and hybrid add-on to adapt to the changed interfaces'''ons.
In addition, Thunderbird will be adding WebExtension support ({{bug|1396172}}) while maintaining "legacy" add-ons '''Questions and hybrid addHelp''': Add-onson developers can get help in the mozilla. dev.apps.thunderbird newsgroup (Note, WebExtension the traditional venue) or in maildev mailing list. (see [[Thunderbird/CommunicationChannels#If_you.27re_a_developer]] Please [[Thunderbird via {{/CommunicationChannels#If_you.27re_a_developer|ask there]] before filing a bug|1396172}} is not yet implmentedreport in bugzilla, because these forums have more people available to help.)
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