I have never been able to authenticate in JOSM. I am running the latest version of JOSM (Revision:19613 Build-Date:2026-08-12 01:46:10) on MacOS Sequoia 15.7.9 with Chrome Version 151.0.7922.172 (Official Build) (x86_64). I have put OSM on Chrome in Remote Control. JOSM seems to work but it won’t authenticate. I haven’t tried editing anything since I’m a JOSM beginner, and I want to be sure I’m logged in and can save my edits. The OAuth 2.0 Authorization does not show up under my OSM account as various other apps do. I get an “Error 400: redirect_uri_mismatch” every time I try to authenticate. I normally use my Google Account to log into OSM, so that’s how I’m trying to authenticate. Any suggestions???
If it’s the same problem as this, it looks like discussion is ongoing.