Manifest V3 Migration Mistakes That Will Cost You Hours (And How to Avoid Them)

Short summary

Chrome extension Manifest V3 migration requires five key pattern changes: async message handlers must return Promises, service workers timeout after 30 seconds so use chrome.alarms for long-running tasks, content scripts must declare their world (MAIN vs. ISOLATED), host permissions must be explicit instead of wildcard, and state must use chrome.storage instead of global variables. The article covers these pitfalls with side-by-side code examples.

• •Message handlers must return Promises, not use synchronous sendResponse
• •Service workers shut down after 30 seconds; use chrome.alarms for keepalive
• •Content script worlds differ: MAIN for DOM access, ISOLATED for chrome APIs

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