Extensions

July 8, 2026 · View on GitHub

Kaset can load browser extensions that work with Safari/WebKit. No extensions are included by default, so you choose what to add.

Managing Extensions

Open Settings (⌘,) and navigate to the Extensions tab.

Adding an Extension

  1. Click the + button in the Extensions tab header.
  2. Choose the extension folder that contains manifest.json.
  3. Kaset adds the extension to the list.
  4. Restart Kaset to load it.

Compatibility: Use a Safari/WebKit version of an extension when one is available. Chrome versions can sometimes work, but not always.

Installing Common Extensions

Kaset adds extension folders. It cannot install directly from the Safari App Store, Chrome Web Store, or a downloaded extension package. You need to choose a folder that contains a file named manifest.json.

Only use extensions from sources you trust.

Best option: use a Safari/WebKit version

If the extension offers a Safari/WebKit download, use that first. Download it, unzip it if needed, then add the folder that contains manifest.json in Settings → Extensions.

Useful official release pages:

Note: Safari extensions from the Mac App Store are usually installed as apps. Kaset cannot add those apps directly. Kaset needs the extension folder itself.

Fallback: copy the extension from Chrome, Edge, or Brave

Use this if you cannot find a Safari/WebKit version.

  1. Install the extension in Chrome, Edge, or Brave:

  2. Find the browser profile folder:

    • Chrome: open chrome://version and copy Profile Path. It is usually ~/Library/Application Support/Google/Chrome/Default.
    • Microsoft Edge: usually ~/Library/Application Support/Microsoft Edge/Default.
    • Brave: usually ~/Library/Application Support/BraveSoftware/Brave-Browser/Default.

  3. In Finder, choose Go → Go to Folder… and open the extension folder:

    <Profile Path>/Extensions/<extension-id>/

    Use these extension IDs:

    ExtensionID
    uBlock Origin Liteddkjiahejlhfcafbddmgiahcphecmpfh
    SponsorBlockmnjggcdmjocbbbhaepdhchncahnbgone

  4. Open the newest version folder inside it. The folder name usually looks like 2026.1.1.0_0 or similar.

  5. Make sure that folder contains manifest.json.

  6. In Kaset, open Settings → Extensions, click +, and choose that version folder.

  7. Restart Kaset when prompted.

Tip: If Kaset shows a version number instead of the extension name, copy that version folder somewhere else, rename the copy to something readable like uBlock Origin Lite, then add the renamed copy to Kaset.

What to expect

  • Extensions only affect Kaset. They do not change Safari, Chrome, or other browsers.
  • YouTube extensions usually affect the YouTube video player. They may not affect YouTube Music unless the extension supports music.youtube.com.
  • If an extension does not work, try a Safari/WebKit version if one exists.
  • Kaset copies the folder you choose. If the extension updates later, remove it from Kaset and add the newer version folder.

Enabling / Disabling an Extension

Toggle the switch next to any extension. The change takes effect after a restart.

Removing an Extension

Click the trash icon next to any extension, then restart Kaset.

Behind the Scenes

  • Kaset keeps its extension list in ~/Library/Application Support/Kaset/extensions.json.
  • When you add an extension, Kaset copies that folder into ~/Library/Application Support/Kaset/ManagedExtensions/.
  • Kaset loads enabled extensions when the app starts.
  • Extensions run inside Kaset's YouTube and YouTube Music web players.

Troubleshooting

  • Manifest not found: Make sure you selected the folder that contains manifest.json.
  • Extension not loading: Restart Kaset after adding or enabling it.
  • Extension updates not appearing: Remove the extension from Kaset, then add the newer version folder.
  • Still stuck: Open Console.app and filter by com.sertacozercan.Kaset, then look for Extensions or WebKit messages.

Architecture

See ADR 0014 for the full architectural decision record.