Marked Quick Look Troubleshooting

Quick Look issues usually fall into one of three categories. Knowing which one you have saves time.

How to tell Marked Quick Look is active: the preview shows styled HTML and an Open in Marked toolbar at the top (when that option is enabled). If you see a different layout, another app's styling, or raw source, a different handler is probably winning.

Work through these before running Terminal commands.

1. Confirm you installed Marked Quick Look, not Marked 3.
2. Confirm the app is in /Applications/Marked Quick Look.app (not in Downloads or on an external volume).
3. Launch Marked Quick Look once from Applications. Do this after every install or update.
4. Test in Finder: select a .md file, then press Spacebar. Some apps trigger Quick Look differently than Finder.
5. Confirm your Mac is running macOS 13 or later.

On macOS Ventura and later:

1. Open System Settings
2. Go to General → Login Items & Extensions → Quick Look Extensions
3. Enable Marked Quick Look Preview
4. Launch Marked Quick Look once from /Applications
5. Try Spacebar on a .md file again

If the extension is disabled or greyed out, toggle it on, launch the container app, and retry.

Run these commands in Terminal (Applications → Utilities → Terminal):

pluginkit -a "/Applications/Marked Quick Look.app/Contents/PlugIns/MarkedQuickLookPreview.appex"
pluginkit -e use -i com.brettterpstra.MarkedQuickLook.preview
killall quicklookd QuickLookUIService 2>/dev/null
qlmanage -r cache

Then relaunch Finder: Option-right-click Finder in the Dock → Relaunch.

Press Spacebar on a .md file again.

pluginkit -m -D -p com.apple.quicklook.preview -A -v | grep -i markdown

You should see com.brettterpstra.MarkedQuickLook.preview in the output. A + prefix means the extension is explicitly enabled.

If Marked Quick Look is missing entirely, reinstall from the App Store, launch the app once, then repeat Step 3.

macOS allows multiple apps to register Markdown Quick Look handlers. Only one extension handles each preview. Another app may be taking precedence over Marked Quick Look.

List registered Markdown preview extensions:

pluginkit -m -D -p com.apple.quicklook.preview -A -v | grep -i markdown

Common conflicting apps

Note: iA Writer does not ship a dedicated Markdown Quick Look extension, but Folder Quick Look, QLMarkdown, and Peek are frequent sources of conflicts because they also target net.daringfireball.markdown.

Test for a conflict

Temporarily disable a suspect extension (example: Folder Quick Look):

pluginkit -e ignore -i studio.appahead.AA7.Markdown-Quick-Look-Extension

Preview a .md file. If Marked Quick Look now works, you have confirmed a conflict.

Restore the other extension:

pluginkit -e default -i studio.appahead.AA7.Markdown-Quick-Look-Extension

Then re-prefer Marked Quick Look:

pluginkit -e use -i com.brettterpstra.MarkedQuickLook.preview

This bypasses Finder and shows whether the extension works at all:

qlmanage -p ~/Desktop/your-file.md

Replace the path with any real .md file.

• Works in Terminal but not Finder: registration or conflict issue (repeat Steps 3–5).
• Fails in both: extension crash or install problem (see Steps 7–8).

If you see unstyled monospace source, macOS is likely falling back to the built-in Text.qlgenerator because the preview extension failed to load.

1. Open Console.app (Applications → Utilities → Console)
2. In the search field, type: MarkedQuickLookPreview
3. Press Spacebar on a .md file in Finder
4. Look for crash reports, sandbox violations, or "extension failed to initialize" messages

If you see errors, note them for a support request (see Step 9).

Marked Quick Look handles files macOS classifies as net.daringfireball.markdown or public.plain-text. Unusual extensions or missing extensions may get a different type.

Check a file's content type:

mdls -name kMDItemContentType ~/path/to/your-file.md

Expected values include net.daringfireball.markdown or public.plain-text. If you see something else (e.g. public.data), macOS may not route the file to any Markdown Quick Look extension.

qlmanage -r cache
qlmanage -r
killall quicklookd QuickLookUIService Finder 2>/dev/null
open -a "Marked Quick Look"

Wait for the app to open, then run:

pluginkit -a "/Applications/Marked Quick Look.app/Contents/PlugIns/MarkedQuickLookPreview.appex"
pluginkit -e use -i com.brettterpstra.MarkedQuickLook.preview

If Quick Look still does not work:

1. Delete Marked Quick Look from /Applications
2. Restart your Mac
3. Reinstall from the Mac App Store
4. Launch the app once
5. Repeat the registration commands above

If you still need help, copy this template, fill it in, and email marked@brettterpstra.com:

macOS version:
(sw_vers output)

Marked Quick Look installed in /Applications:
(yes/no)

Launched Marked Quick Look after install:
(yes/no)

What happens when you press Spacebar:
(no panel / plain text / styled preview from another app)

Other Markdown or Quick Look apps installed:
(list any from the conflict table above)

Output of:
pluginkit -m -D -p com.apple.quicklook.preview -A -v | grep -i -E "Marked|markdown"

Console errors (if any):
(paste from Console.app while previewing)

Most first-day issues are resolved by launching the app once and re-registering the extension:

open -a "Marked Quick Look"
pluginkit -a "/Applications/Marked Quick Look.app/Contents/PlugIns/MarkedQuickLookPreview.appex"
pluginkit -e use -i com.brettterpstra.MarkedQuickLook.preview
killall quicklookd QuickLookUIService 2>/dev/null
qlmanage -r cache

Then press Spacebar on a .md file in Finder.