When Firefox is running it normally starts a remoting server that allows other Firefox instances to communicate with it. When a new instance of Firefox starts it uses a remoting client to detect if an existing instance is already running and if so pass any command line arguments to it so only one instance is ever running for a given profile. We have for a long time had a `-no-remote` command line argument that disables both remoting server and client. Prior to Firefox 67 this was used for running multiple instances of Firefox at the same time however now the remoting system is scoped to the profile in use so as long as you are running with different profiles you do not need the `-no-remote` command line argument. We also support a `-new-instance` argument which disables just the remoting client at startup and so allows startup to proceed ignoring any running instances using the same profile. Using either of these arguments when there is already a running instance results in the user seeing a dialog explaining that the profile is in use and (on some platforms) offering to kill the existing instance. Many tools and documentation still recommend using the `-no-remote` argument and it has caused unexpected behaviour in the past causing users to file bugs and support requests. Additionally we plan to make more use of the remoting system to support the new multiple profiles feature. In order to remove this confusing footgun and so we can rely on the remoting server always be enabled in any running instance of Firefox I am planning on removing the `-no-remote` command line argument from Firefox. Note that the `-new-instance` command line argument will remain.
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When Firefox is running it normally starts a remoting server that allows other Firefox instances to communicate with it. When a new instance of Firefox starts it uses a remoting client to detect if an existing instance is already running and if so pass any command line arguments to it so only one instance is ever running for a given profile. We have for a long time had a `-no-remote` command line argument that disables both remoting server and client. Prior to Firefox 67 this was used for running multiple instances of Firefox at the same time however now the remoting system is scoped to the profile in use so as long as you are running with different profiles you do not need the `-no-remote` command line argument. We also support a `-new-instance` argument which disables just the remoting client at startup and so allows startup to proceed ignoring any running instances using the same profile. Using either of these arguments when there is already a running instance results in the user seeing a dialog explaining that the profile is in use and (on some platforms) offering to kill the existing instance. Many tools and documentation still recommend using the `-no-remote` argument and it has caused unexpected behaviour in the past causing users to file bugs and support requests. Additionally we plan to make more use of the remoting system to support the new multiple profiles feature. In order to remove this confusing footgun and so we can rely on the remoting server always be enabled in any running instance of Firefox I am planning on removing the `-no-remote` command line argument from Firefox. Note that the `-new-instance` command line argument will remain. This would also include removing the `MOZ_NO_REMOTE` environment variable which does the same thing as the `-no-remote` command line argument.