When I built Weather & Clock Dashboard , I wanted to understand the current state of Firefox extension APIs versus Chrome's Manifest V3 changes.

Here's what I learned.

Quick Context: Why MV3 Matters

Manifest V3 is Google's overhaul of the Chrome extension platform. It's controversial because some changes limit ad-blockers and general-purpose content filtering.

Firefox's position : Mozilla implemented MV3 for compatibility, but with key differences that preserve extension power.

What Changed in MV3

1. Background Scripts → Service Workers

MV2:

"background" : { "scripts" : [ "background.js" ], "persistent" : false }

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MV3:

"background" : { "service_worker" : "background.js" }

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Service workers are ephemeral — they don't persist in memory.…