MP4 videos may open in QuickTime Player or another installed app. If you prefer IINA’s playback interface, make it the opener for local .mp4 files. The MP4 container can hold different codecs, so test a representative video first.
Method 1: Use Finder
- In Finder, select a sample file such as video.mp4.
- Press Command–I, or choose File → Get Info.
- Expand Open with and choose IINA. If it is missing, choose Other and locate the installed app.
- Click Change All and confirm the macOS prompt.
- Double-click another file of the same type to check the new default.
Method 2: Manage associations with Pahkui
Pahkui lets you browse by app or by format. When setting up an editor for several file types, you can inspect the current defaults and review pending changes in one window. Requires macOS 14 or later.
- Open Pahkui, switch to Format, and search for the extension you need from .mp4.
- Select IINA. Use Choose another app if it is not listed.
- Review the pending association, click Apply changes, and confirm the new app in the macOS dialog.
The formats in this guide can be configured with Pahkui Free. The manual Finder method does not require a purchase. See pricing
If the default app does not change
- The default affects saved .mp4 files, not videos embedded in Safari or another browser.
- A protected or unsupported video may still fail in IINA; the association does not remove protection or replace codecs.
- If IINA is missing, confirm it is installed and can open the sample directly, then locate it with Other. If an extension is absent from the catalog, add the format in Pahkui. Changing an association does not add format support to the target app.
Common questions
Will this change online streaming playback?
No. It selects the player for local files opened from Finder, not a website’s embedded player.
How do I restore the previous app for .mp4?
Choose the previous app again in Finder or Pahkui and confirm the change. This updates the type association without deleting files. Use the Open With context menu for a one-time exception.