---
title: Chromium "Show in folder" fails with '"." is not a valid folder' (opens Baobab)
date: 2026-04-14
summary: Clicking the folder icon in Chromium's downloads panel gave '"." is not a valid folder'. Baobab (GNOME Disk Usage Analyzer) was the default handler for inode/directory, so xdg-open launched it. Making a file manager the default in ~/.config/mimeapps.list fixed it.
tags: chromium, xdg, mime, baobab, lxqt, arch
environment: Arch Linux; Chromium; LXQt desktop session (started via Chrome Remote Desktop); Baobab and pcmanfm-qt installed
author: shaun, written up with Claude
status: published
---

## Symptoms

In Chromium's downloads panel, clicking the folder icon next to a downloaded file ("Show in
folder") did not open a file manager. Instead this error appeared:

```text
"." is not a valid folder
```

## Root cause

On Linux, Chromium hands "show in folder" to `xdg-open`, which picks the default application
for the MIME type `inode/directory`.

Baobab (GNOME Disk Usage Analyzer) declares that MIME type in its desktop file,
`/usr/share/applications/org.gnome.baobab.desktop`:

```ini
MimeType=inode/directory;
```

With no user-level default set, Baobab won:

```text
$ xdg-mime query default inode/directory
org.gnome.baobab.desktop
```

So `xdg-open` launched Baobab, which expects a folder to scan, not to browse, and rejected
the `"."` argument with the error above.

This happened in an LXQt session. Our guess (not tested elsewhere) is that it is most likely
on non-GNOME desktops, where nothing else sets a user default for directories, so Baobab's
system-wide claim is the one that gets picked.

## Fix

Make your file manager the user-level default for `inode/directory` in
`~/.config/mimeapps.list`. With pcmanfm-qt (LXQt's file manager):

```ini
[Default Applications]
inode/directory=pcmanfm-qt.desktop;

[Added Associations]
inode/directory=pcmanfm-qt.desktop;
```

Or with `xdg-mime`, which writes the `[Default Applications]` entry for you:

```bash
xdg-mime default pcmanfm-qt.desktop inode/directory
```

Use the desktop file of whatever file manager you have (`thunar.desktop`,
`org.gnome.Nautilus.desktop`, `pcmanfm.desktop`, …).

Verify:

```text
$ xdg-mime query default inode/directory
pcmanfm-qt.desktop
```

No restart was needed; the next "Show in folder" click opened the file manager.

The fix used on the affected machine was the `mimeapps.list` edit; the `xdg-mime default`
one-liner is the standard equivalent but was not the command actually run.