SUMMARY After registering site custom protocol handler it does not work and opens external application instead. STEPS TO REPRODUCE 1. Register a scheme handler 2. Try to use it (click on link with registered protocol) 3. Observe OBSERVED RESULT External commands is started, in case Falkon is registered to handle the registered protocol it will spawn an infinite amount of tabs. EXPECTED RESULT Redirected to the page specified in protocol handler ADDITIONAL INFORMATION After adding the protocol/scheme to the allowed list in [Preferences > Other > Custom Scheme Manager > Allowed Schemes (Add)] and restarting Falkon, it opens a single page with "about:blank#blocked" address in addressbar.
Results of my investigation: - The scheme of the protocol handler "web+whatever" cannot be in the allowed/registered schemes. If it is registered as a custom scheme it will redirect to "about:blank#blocked" - Falkons code to handle custom protocols is executed when the custom protocol handler is requested and also when browser starts, but somehow it is not working properly. - If the Falkon custom code is bypassed and the request is accepted on the first try (with or without blocking popup), the feature works correctly, but makes the protocol handler only a temporary thing which needs to be registered after each browser restart (which is not a nice thing). - I tested Qutebrowser if it works there and it does not seem to register it on its own after browser starts, I need to go to the site and than it will register it. Maybe this is the intended way of using it? First go to the site which offers protocol handler and then continue browsing? (can be done with pinned tabs and automaed answering within Falkon), This is how qutebrowser does it, from what I understand. (Or I missed something) So I am still in doubts on how this thing should be working.
A possibly relevant merge request was started @ https://invent.kde.org/network/falkon/-/merge_requests/151
Git commit 577aaff46281a004519819bcf24d6f3b688246a8 by Juraj Oravec. Committed on 08/10/2025 at 19:42. Pushed by jurajo into branch 'master'. Fix web custom protocol handler registration FIXED-IN: 25.12.0 Signed-off-by: Juraj Oravec <jurajoravec@mailo.com> M +3 -1 src/lib/other/protocolhandlermanager.cpp https://invent.kde.org/network/falkon/-/commit/577aaff46281a004519819bcf24d6f3b688246a8