I try to launch Firefox over SSH, using

ssh -X user@hostname

and then

firefox -no-remote

but it's very very slow.

How can I fix this? Is it a connection problem?

  • 3
    Unless you have some incredibly high level of encryption or the server you're ssh'ing into has a high load, it's probably not the ssh part of the equation. It's usually a bandwidth and/or latency issue. – Bratchley Feb 28 '15 at 17:17
  • 1
    Take a look at this: stackoverflow.com/q/12977879/252489 – Gowtham Feb 28 '15 at 17:24
  • @Gowtham so i can use: ssh -X -C user@hostname ? – DevOps85 Feb 28 '15 at 17:29

The default ssh settings make for a pretty slow connection. Try the following instead:

ssh -YC4c arcfour,blowfish-cbc user@hostname firefox -no-remote

The options used are:

-Y      Enables trusted X11 forwarding.  Trusted X11 forwardings are not
         subjected to the X11 SECURITY extension controls.
 -C      Requests compression of all data (including stdin, stdout,
         stderr, and data for forwarded X11 and TCP connections).  The
         compression algorithm is the same used by gzip(1), and the
         “level” can be controlled by the CompressionLevel option for pro‐
         tocol version 1.  Compression is desirable on modem lines and
         other slow connections, but will only slow down things on fast
         networks.  The default value can be set on a host-by-host basis
         in the configuration files; see the Compression option.
 -4      Forces ssh to use IPv4 addresses only.
 -c cipher_spec
         Selects the cipher specification for encrypting the session.

         For protocol version 2, cipher_spec is a comma-separated list of
         ciphers listed in order of preference.  See the Ciphers keyword
         in ssh_config(5) for more information.

The main point here is to use a different encryption cypher, in this case arcfour which is faster than the default, and to compress the data being transferred.

NOTE: I am very, very far from an expert on this. The command above is what I use after finding it on a blog post somewhere and I have noticed a huge improvement in speed. I am sure the various commenters below know what they're talking about and that these encryption cyphers might not be the best ones. It is very likely that the only bit of this answer that is truly relevant is using the -C switch to compress the data being transferred.

  • 11
    Actually by changing the encryption settings you can improve the throughput of the connection, but that will have almost no influence on the latency which is what makes the X-over-ssh connection so slow... Or said otherwise: you can achieve to transfer a file faster, but the time it takes to start transferring will not change (almost). That is the problem of the X-protocol, it involves a lot of messages and acknowledgements between the client and the server, so over internet the few milliseconds latency get multiplied many times until you can see a button change its status for instance. – Ariel Feb 28 '15 at 20:44
  • 8
    Is -4 (IPv4) really relevant here? – Cornstalks Feb 28 '15 at 20:57
  • 6
    The `arcfour" cipher is deprecated, btw. – Martin Schröder Feb 28 '15 at 23:39
  • 5
    Compression helps, but doesn't work miracles. Firefox is very demanding. Changing the cipher is unlikely to make a difference unless one of the sides is very very limited in CPU time: with high-end devices such as smartphones and PCs, encryption/decryption time is negligible compared to network latency and bandwidth. – Gilles Mar 1 '15 at 0:55
  • 6
    The ciphers suggested are the wrong way to go. As Gilles says, the majority of devices these days will have no problem at all with the default AES-CTR: it is very fast, especially if the hardware used has the AES instruction set. RC4 is weak and being phased out across the net, and Blowfish-CBC may not necessarily be faster than AES-CTR anyway. – Reid Mar 1 '15 at 1:51

One of the biggest issues when launching some X-client remotely is the X-protocol, not so much the ssh overhead! The X-protocol requires a lot of ping-pong'ing between the client and the server which absolutely kills performance in the case of remote applications.

Try something like "x2go" (which also goes over ssh with default setups) in you will notice that firefox "flies" in comparison!

Several distributions provide the x2go packages out of the box, for instance Debian testing, or in Stable-Backports. But if not, see http://wiki.x2go.org/doku.php/download:start , they provide prebuilt binary packages/repositories for many distributions. You should install x2goclient (on the computer where you want to 'use' firefox) and x2goserver (in the computer where firefox should be running), you can then configure your sessions for single X applications of for full desktop views etc. The connection itself happens over ssh. It's a really wonderful tool :)

To use it, you run "x2goclient", it starts a GUI where you can create a new session: you provide the dns name of the server, port, ssh data, etc and then you select the "session type", ie, if you want a full remote KDE or GNOME desktop for instance, or just a "single application" and there you enter "firefox".

  • 1
    how i can try x2go? the command – DevOps85 Feb 28 '15 at 18:00
  • 3
    There seems to be no x2goserver package on Debian (or Ubuntu). Also, can this be configured to allow tunneling? For example, I use machineX but I can only ssh to it via machineY. Could x2go deal with that? – terdon Feb 28 '15 at 18:15
  • @terdon you are right, i checked just the client. But you can just add the x2go repository (see the link wiki.x2go.org/doku.php/download:start) and the server is there. I don't know why only the client is in Debian. Tunneling: for sure it is possible, but never tried it. I'd expect it should be enough to just configure ssh in ~/.ssh/config and use the right (tunneled) hostname in your x2go session. – Ariel Feb 28 '15 at 20:03
  • @terdon: there is a "Use proxy server for SSH connection" (ssh/http) option in the x2go session configuration. So that should do the trick also! – Ariel Feb 28 '15 at 20:09
  • This seems interesting, I'll play with it some more. So far I can confirm that configuring the tunnel in .ssh/config is not enough. I have it setup so that ssh machineB actually runs via a tunnel through machineA but x2go does not seem to see it. – terdon Feb 28 '15 at 20:11

I have much better experience in using an ssh tunnel to route traffic through another machine. It's very easy to set up since you have ssh access anyway. In a terminal on your computer, type

ssh -vv -ND 8080 user@yourserver

Keep this window open and watch it delivering some verbose messages about the data flowing through the tunnel.

In firefox, go to Preferences -> Advanced -> Network -> Connection: Settings.

Select Manual proxy configuration and add a SOCKS v5 proxy:

 SOCKS Host:   localhost    Port 8080

Check your new IP by navigating to e.g. http://whatismyipaddress.com/.

You can use a firefox add-on like foxy proxy to dynamically switch proxies.

  • Upvoted, this a very valid alternative to using NX-based compression (x2go etc), much more useful than fiddling with ssh encryption settings :) – Ariel Mar 4 '15 at 21:01
  • I used always ssh -L 8080:localhost:8080, but liked the -ND option but not sure why you used Dinamic instead or Remote or Listen. By the way, using proxy it's much better than use -X, but, I think the better way is to use VNC if you need more X programs and not just Firefox. – erm3nda Apr 6 '16 at 2:57
  • easy to setup and works efficiently! – david.perez Feb 22 at 10:17

Firefox so slow over SSH because newer builds of firefox allow multiple instances.If you have bandwidth problems, use a light browser like dillo and you willl not even notice the connection speed.


Another thing that will improve your browsing over ssh is to enable pipelining in Firefox. Open about:config and change network.http.pipelining to true.

  • That option should make the loading of webpages faster, but is completely unrelated to the fact that the browser is running over an SSH tunnel or not. Anyways, beware of the "but's" when you touch advanced options... see kb.mozillazine.org/Network.http.pipelining – Ariel Mar 4 '15 at 11:10
  • In my experience browsing over ssh gets slow and pipelining requests is a big help since otherwise any given request has to wait for previous ones which may or may not complete in a timely manner if at all. I also combine this with ssh multiplexing. It makes a noticeable difference. Turning off pipelining goes back to being unbearably slow in my case. – Tanath Mar 5 '15 at 2:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.