Building a Firefox New Tab Extension: From Idea to AMO Publishing

Every time you open a new tab in Firefox, there's a missed opportunity. The default page is... fine. But what if it showed you the weather, your world clocks, and a search bar — all without any data leaving your device?

That's what I built with Weather & Clock Dashboard . Here's how the whole thing came together, including the surprising parts of publishing to AMO (addons.mozilla.org).

The manifest.json entry point

A new tab override is deceptively simple:

{ "manifest_version" : 2 , "name" : "Weather & Clock Dashboard" , "version" : "1.0" , "chrome_url_overrides" : { "newtab" : "newtab.html" }, "permissions" : [ "storage" ] }

Enter fullscreen mode

Exit fullscreen mode

One file override, one permission. That's it.

Fetching weather without a backend

Most weather APIs require server-side secrets.…