wxt/docs/get-started/build-targets.md

Build Targets

You can build an extension for any combination of browser and manifest verison. Different browsers and manifest versions support different APIs and entrypoints, so be sure to check that your extension functions as expected for each target.

Separate build targets are written to their own output directories:

<rootDir>
└─ .output
   ├─ chrome-mv3
   ├─ firefox-mv2
   ├─ edge-mv3
   └─ ...

Target Browser

To build for a specific browser, pass the -b --browser flag from the CLI:

wxt --browser firefox
wxt build --browser firefox

By default, it will build for chrome. When excluding the --mv2 or --mv3 flags, it will default to the commonly accepted manifest version used with that browser.

Browser	Default Manifest Version
chrome	3
firefox	2
safari	2
edge	3
Any other string	3

Target Manifest Version

To build for a specific manifest version, pass either the --mv2 flag or --mv3 flag from the CLI.

wxt --mv2
wxt build --mv2

When the -b --browser flag is not passed, it defaults to chrome. So here, we're targetting MV2 for Chrome.