The best way to Inject a International with Net Extensions in Manifest V3


    For these of you not acquainted with the world of net extension growth, a storm is brewing with Chrome. Google will cease help for manifest model 2, which is what the overwhelming majority of net extensions use. Manifest model 3 sees many modifications however the largest change is transferring from persistent background scripts to service employees. This…is…a…large…change.

    Modifications from manifest model 2 to model 3 embrace:

    • Going from persistent background script to a service employee that may die after 5 minutes
    • No use of <iframe> components or different DOM APIs from the service employee
    • All APIs have grow to be Promise-based
    • Restrictions on content material from a CSP perspective

    One perform that net extensions typically make use of is executing scripts upon every new web page load. For an online extension like MetaMask, we have to present a worldwide window.ethereum for dApps to make use of. So how can we do this with manifest model 3?

    As of Chrome v102, builders can outline a world property with a worth of remoted or important (within the web page) for content material scripts. Whereas builders ought to outline content_scripts within the extension’s manifest.json file, the important worth actually solely works (on account of a Chrome bug) while you programmatically outline it from the service employee:

    await chrome.scripting.registerContentScripts([
        id: 'inpage',
        matches: ['http://*/*', 'https://*/*'],
        js: ['in-page.js'],
        runAt: 'document_start',
        world: 'MAIN',

    Within the instance above, in-page.js is injected and executed inside the principle content material tab each time a brand new web page is loaded. This in-page.js file units window.ethereum for all dApps to make use of. If the world is undefined or remoted, the script would nonetheless execute however would accomplish that in an remoted setting.

    Manifest model 3 work is sort of the slog so please hug your closest extension developer. There are lots of big structural modifications and navigating these modifications is a brutal push!


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