Make spaceMD the default Markdown viewer

Setting spaceMD as the default app makes a double-clicked Markdown file open in the spaceMD viewer. It can also make Finder use the spaceMD document icon for that file type. This setting is separate from Quick Look.

spaceMD does not edit Markdown. After changing the default, use Open With when you want to send a file to your editor.

Before you change the default

Decide which action you want from a double click:

• choose spaceMD if double clicks should open a formatted reading view
• keep your editor as default if double clicks should start editing immediately

Quick Look does not depend on this choice. Selecting a file and pressing the Space bar can use the spaceMD Quick Look extension while another app remains the default editor.

Set spaceMD as the default

1. In Finder, select a Markdown file.
2. Press Command-I to open its Info window.
3. Expand Open with if the section is closed.
4. Choose spaceMD from the app menu.
5. Select Change All if Finder should use spaceMD for all files of that type.
6. Confirm the macOS question.
7. Close the Info window.

Double-click a Markdown file with the same type to check the result. The file should open in the spaceMD viewer. It remains unchanged on disk.

macOS can treat different filename extensions as related to the same Markdown type, but the association shown in the Info window is the reliable result for the selected file. Repeat the process for another supported extension if macOS keeps a separate association for it.

Open a file in your editor

When spaceMD is the default:

1. Control-click the Markdown file in Finder.
2. Open Open With.
3. Choose your editor.

This opens the selected file in the editor without changing the default for every future file.

Restore an editor as the default

1. Select a Markdown file in Finder.
2. Press Command-I.
3. Under Open with, choose the editor you want.
4. Select Change All.
5. Confirm the change.

Double-click another Markdown file to verify that the editor opens again. The spaceMD viewer remains available through Open With.

Why the document icon changes

Finder normally shows the document icon supplied by the default app for a file type. spaceMD includes an icon for Markdown documents, so it can appear after spaceMD becomes the default. macOS caches icons and may not update every Finder window immediately.

The icon is not a rendered preview of the file's contents. macOS does not call the spaceMD thumbnail extension for Markdown text files. Changing the default app can change the fixed document icon, but it does not create a content-based thumbnail.

If it does not work

spaceMD is missing from Open with: Confirm that spaceMD is installed in the Applications folder and launch it once. Then reopen the file's Info window.

Only one file opens in spaceMD: Choosing spaceMD from Open With affects that one action. Use Command-I and Change All to change the default for the file type.

The old icon remains: Close and reopen the Finder window, then allow macOS time to update its icon cache. The opening behaviour is a better check than the icon alone.

Quick Look did not change: That is expected. Default-app association and Quick Look are separate. Follow Set up formatted Markdown in Quick Look to enable the formatted Space bar preview.