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Manifest V3 (MV3) is the current, required standard for building and publishing Chrome extensions. If you’ve browsed extension tutorials recently, you’ve likely seen it mentioned — and with good reason. Google now requires MV3 for all new Chrome Web Store submissions. Extensy generates MV3 extensions by default, so you never have to deal with the architectural details manually.

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Why Google introduced MV3

Chrome introduced MV3 to make extensions safer, more private, and less resource-intensive for users.

Security

MV3 prevents remote code execution. Every line of code your extension runs must be bundled inside the submitted ZIP file — no downloading scripts at runtime.

Privacy

MV3 introduces more granular permissions, giving users clearer control over which sites an extension can access.

Performance

MV3 replaces persistent background pages with event-driven service workers that only run when needed, saving battery and memory.

CWS requirement

Google has deprecated MV2 and requires MV3 for all new submissions and renewals on the Chrome Web Store.

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MV2 vs. MV3: key differences

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How Extensy handles MV3 for you

Building MV3 extensions manually is tricky — service worker lifetimes are short, the declarativeNetRequest API requires static rule files, and older patterns like eval() are outright banned. Extensy takes care of all of this automatically:
1

Automatic service workers

Extensy generates a correctly structured background.js service worker, including the event listeners Chrome expects.
2

Minimum-privilege permissions

Your manifest only requests the permissions that match your prompt — nothing more.
3

Modern action API

Extensy always uses the unified action key instead of the deprecated browser_action or page_action keys.
4

No remote code

All generated code is bundled locally at build time, keeping your extension fully compliant with MV3 security rules.

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Watch out for outdated tutorials

StackOverflow and older blog posts are full of MV2 examples. The two clearest warning signs are:
  • A background.html file referenced in the manifest
  • webRequest used to block or redirect URLs
If a tutorial references chrome.extension.getBackgroundPage() or sets "manifest_version": 2, it is using an outdated MV2 pattern. Extensy’s generated code always uses the correct MV3 equivalents.
MV3 prohibits eval() and runtime code-string injection. If you manually add these patterns to an Extensy extension, the Chrome Web Store will reject your submission.
You never need to configure MV3 settings manually when using Extensy. The service worker lifecycle, declarative rules, and permission scoping are all handled for you behind the scenes.