How to configure a thumbnailer for preview

[galou]

What system are you running Yazi on?

Linux Wayland

What terminal are you running Yazi in?

kitty 0.42.2

yazi --debug output

Yazi
    Version: 25.6.11 (81a0cf4a 2025-09-08)
    Debug  : false
    Triple : x86_64-unknown-linux-gnu (linux-x86_64)
    Rustc  : 1.89.0 (29483883 2025-08-04)

Ya
    Version: 25.6.11 (81a0cf4a 2025-09-08)

Emulator
    TERM                : Some("xterm-kitty")
    TERM_PROGRAM        : None
    TERM_PROGRAM_VERSION: None
    Brand.from_env      : Some(Kitty)
    Emulator.detect     : Emulator { kind: Left(Kitty), light: false, csi_16t: (8, 21), force_16t: false }

Adapter
    Adapter.matches    : Kgp
    Dimension.available: Dimension { rows: 59, columns: 303, width: 2424, height: 1239 }

Desktop
    XDG_SESSION_TYPE           : Some("wayland")
    WAYLAND_DISPLAY            : Some("wayland-1")
    DISPLAY                    : Some(":0")
    SWAYSOCK                   : Some("/run/user/1000/sway-ipc.1000.3030.sock")
    HYPRLAND_INSTANCE_SIGNATURE: None
    WAYFIRE_SOCKET             : None

SSH
    shared.in_ssh_connection: false

WSL
    WSL: false

Variables
    SHELL           : Some("/usr/bin/zsh")
    EDITOR          : Some("vim")
    VISUAL          : None
    YAZI_FILE_ONE   : None
    YAZI_CONFIG_HOME: None
    YAZI_ZOXIDE_OPTS: None
    FZF_DEFAULT_OPTS: None

Text Opener
    default     : Some(OpenerRule { run: "${EDITOR:=vi} \"$@\"", block: true, orphan: false, desc: "$EDITOR", for: None, spread: true })
    block-create: Some(OpenerRule { run: "${EDITOR:=vi} \"$@\"", block: true, orphan: false, desc: "$EDITOR", for: None, spread: true })
    block-rename: Some(OpenerRule { run: "${EDITOR:=vi} \"$@\"", block: true, orphan: false, desc: "$EDITOR", for: None, spread: true })

Multiplexers
    TMUX               : false
    tmux version       : tmux 3.2a
    tmux build flags   : enable-sixel=Unknown
    ZELLIJ_SESSION_NAME: None
    Zellij version     : No such file or directory (os error 2)

Dependencies
    file          : 5.41
    ueberzugpp    : No such file or directory (os error 2)
    ffmpeg/ffprobe: 4.4.2-0 / 4.4.2-0
    pdftoppm      : 22.02.0
    magick        : No such file or directory (os error 2)
    fzf           : 0.54.3
    fd/fdfind     : 8.3.1 / 8.3.1
    rg            : 13.0.0
    chafa         : 1.8.0
    zoxide        : 0.9.4
    7zz/7z        : No such file or directory (os error 2) / 16.02
    resvg         : 0.45.1
    jq            : 1.6

Clipboard
    wl-copy/paste: 2.0.0 / 2.0.0
    xclip        : 0.13
    xsel         : 1.2.0

Routine
    `file -bL --mime-type`: text/plain


See https://yazi-rs.github.io/docs/plugins/overview#debugging on how to enable logging or debug runtime errors.

Describe the question

I'd like to use a "standardized" thumbnailer for a specific type of file. By "standardized" I mean that I guess it respects XDG standards. Concretely, I want to use a thumbnailer for FreeCAD.

~/.local/share/thumbnailers/FreeCAD.thumbnailer:

[Thumbnailer Entry]
TryExec=/home/gael/80-build/freecad/freecad-thumbnailer
Exec=/home/gael/80-build/freecad/freecad-thumbnailer -s %s %i %o
MimeType=application/x-extension-fcstd;

I don't know how but the thumbnailer works in Caja, though I have the impression that the FreeCAD.thumbnailer file in the package freecad-daily-common is broken because its Exec entry points to a non-existing file. Nevertheless, image preview of FreeCAD files (*.fcstd extension) works in Caja.

Thanks!

Anything else?

No response

Checklist

• I have read all the documentation
• I have searched the existing discussions/issues

[galou]

I forgot to add what I tried:

[plugin]
prepend_previewers = [
	# FreeCAD
	{ mime = "application/x-extension-fcstd", run = "image" },
]

[sxyazi]

Yazi does not use the XDG thumbnailer because that is Linux-specific and Yazi is cross‑platform (Linux, macOS, Windows, Android). However, @Sonico98 has an awesome plugin allmytoes.yazi, which uses freedesktop‑compatible thumbnails, which might be what you're looking for.

Also, Yazi's built‑in image uses image‑rs as the image decoding backend and it does not support FreeCAD. For that purpose you need a dedicated custom previewer.

Note that Yazi does not use the deprecated x- prefix for MIME types to work around file(1) cross‑version compatibility, so your application/x-extension-fcstd will never be matched. Instead, spot the file's MIME type (Tab key by default).

[galou]

allmytoes.yazi is probably what I'm looking for and I even had it installed ;)

I don't understand your point with image-rs, thumbnails are PNG images.

Unfortunately, spot says that my file is a application/zip, which of course it secondarily is. Is spot the tool that is used to determine the MIME type? mimetype on Linux says application/x-extension-fcstd on Pop!0S_22.04 (based on Ubuntu 22.04). file -bL --mime-type says application/zip.

I'll see who I need to persuade that *.fcstd files are FreeCAD files in Yazi or allmytoes.