Save as GIF

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 3,
  "name": "Save as GIF",
  "version": "1.0",
  "description": "Download GIF images as .gif format",
  "permissions": [
    "activeTab",
    "contextMenus",
    "downloads"
  ],
  "background": {
    "service_worker": "background.js"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "action": {
    "default_icon": {
      "48": "icon.png"
    }
  },
  "icons": {
    "48": "icon.png"
  }
}