Since v14, Flameshot captures the screen through the XDG Desktop Portal (org.freedesktop.portal.Desktop), including on X11. Full desktop environments such as GNOME and KDE Plasma ship a portal backend that implements the org.freedesktop.impl.portal.Screenshot interface, so capturing works out of the box.
Minimal X11 window managers (i3, dwm, xmonad, bspwm, qtile, AwesomeWM, ...) usually do not provide such a backend: either no xdg-desktop-portal backend is running, or the backend that is installed (for example xdg-desktop-portal-gtk) does not implement the Screenshot interface. In that case the capture fails.
When the portal service cannot be reached:
flameshot: error: Could not locate the `org.freedesktop.portal.Desktop` service
flameshot: error: Unable to capture screen
flameshot: info: Screenshot aborted.
When a portal backend is present but does not implement the Screenshot interface (for example only xdg-desktop-portal-gtk is installed):
flameshot: error: The xdg-desktop-portal backend did not respond If you are on
wayland make sure an xdg-desktop-portal backend for your desktop is installed
and properly configured.
If on X11 enable Legacy X11 method in the General Settings
In both cases the Flameshot capture overlay never appears.
Flameshot ships a built-in option that bypasses the portal and uses Qt's native X11 capture (the method used before v14). Enable it once and capturing works again.
Note
This option only affects X11 sessions; it is ignored on Wayland.
Open Configuration → General and tick "Use legacy X11 screenshot method".
Edit ~/.config/flameshot/flameshot.ini and add, under the [General] section:
[General]
useX11LegacyScreenshot=trueThen restart the Flameshot tray daemon so the new setting is picked up:
killall flameshot 2>/dev/null; flameshot &Not every xdg-desktop-portal backend implements org.freedesktop.impl.portal.Screenshot. Notably, the generic GTK backend (xdg-desktop-portal-gtk) does not, while the GNOME and KDE backends do but rely on their respective compositors (GNOME Shell / KWin), which are not running under a minimal window manager.
See the list of backends and interfaces on the Arch Wiki to check whether your installed backend supports the Screenshot interface.
The following X11 window managers have been reported to need the legacy option: i3, dwm, xmonad, bspwm, qtile, AwesomeWM, Xfce4, and Plasma on X11.
Q) I enabled the legacy option but the capture window is not full screen / behaves like a normal window.
A) Some window managers tile or decorate the Flameshot window. Add a floating, borderless, fullscreen rule for the flameshot window class in your window manager configuration (similar to the rules documented for Sway / wlroots).