Extension APIs

epos.browser provides access to chrome.* APIs in every context of your extension.

Normally, you cannot access chrome.* from web pages or iframes. And in isolated content scripts, access is very limited. Epos removes these boundaries and lets you use the same APIs from any context.

Why epos.browser and not epos.chrome?

There are two reasons for the name:

1. There is an ongoing effort to standardize the extensions API, and browser is the common name used for it.

2. chrome sounds Chrome-specific, but Epos also works with other Chromium browsers, including Edge and Brave. In that context, browser is a better fit.

The Same APIs

epos.browser does not give you a new APIs to learn. It is a one-to-one mirror of chrome.*. For example:

const tabs = await epos.browser.tabs.query({ active: true })

epos.browser.windows.onCreated.addListener(window => {
  console.log('New window:', window.id)
})

If you know how to use chrome.*, you already know how to use epos.browser.*.

epos.browser is fully typed, so you get autocompletion and type checking in your editor.

To learn more, see the Chrome Extensions API reference or the MDN version.

WARNING

When using Epos, you can not access chrome directly. Always use epos.browser.

Permissions Still Apply

epos.browser does not bypass the extension's permission system. If an API requires a permission, it still requires that permission when accessed via epos.browser.

For example, epos.browser.downloads.* needs the downloads permission, and epos.browser.cookies.* needs the cookies permission.

To request or inspect permissions at runtime, use epos.browser.permissions.request():

main.ts

const granted = await epos.browser.permissions.request({
  permissions: ['downloads'],
})

if (granted) {
  await epos.browser.downloads.download({
    url: 'https://example.com/file.txt',
    filename: 'file.txt',
  })
}

epos.json

{
  "name": "My Extension",
  "optionalPermissions": ["downloads"],
  "matches": "<popup>",
  "load": "main.js"
}

To learn more about permissions, see the Permissions guide.

Supported APIs

epos.browser does not support the full set of chrome APIs, but it does include the most commonly used ones:

• action
• alarms
• browsingData
• contextMenus
• cookies
• declarativeNetRequest
• downloads
• extension
• i18n
• management
• notifications
• permissions
• runtime
• sidePanel
• storage
• tabs
• webNavigation
• windows