# Run Cylc gui on a different port

**URL:** <https://cylc.discourse.group/t/run-cylc-gui-on-a-different-port/1182>\
**Category:** Cylc Support\
**Created:** [June 5, 2025, 9:15am UTC](https://cylc.discourse.group/t/run-cylc-gui-on-a-different-port/1182 "2025-06-05T09:15:23Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![cazria](https://avatars.discourse-cdn.com/v4/letter/c/dfb087/32.png) [@cazria](https://cylc.discourse.group/u/cazria)\
**Post date:** [June 5, 2025, 9:15am UTC](https://cylc.discourse.group/t/run-cylc-gui-on-a-different-port/1182/1 "2025-06-05T09:15:23Z")

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Hi,  
I’d like to launch the Cylc GUI on a specific port because several ports are already in use on the server I’m working on. Currently, it starts on a different port each time, which makes it a bit unpredictable.

Is there an option like `cylc gui --port` to set the port manually? Or maybe a configuration file I can modify to define a fixed port?

Thanks in advance!  
Chloé Azria

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<div class="post-metadata">

**Author:** ![oliver.sanders](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/oliver.sanders/32/110_2.png) [@oliver.sanders](https://cylc.discourse.group/u/oliver.sanders)\
**Post date:** [June 5, 2025, 11:13am UTC](https://cylc.discourse.group/t/run-cylc-gui-on-a-different-port/1182/2 "2025-06-05T11:13:47Z")

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Yes, you guessed right, it’s `cylc gui --port=<port>`.

There is also a Jupyter Server configuration for this - `ServerApp.port` ([jupyter server configs](https://jupyter-server.readthedocs.io/en/latest/other/full-config.html#other-full-config)).

---

<div class="post-metadata">

**Author:** ![hilary.j.oliver](https://yyz2.discourse-cdn.com/free1/user_avatar/cylc.discourse.group/hilary.j.oliver/32/4_2.png) [@hilary.j.oliver](https://cylc.discourse.group/u/hilary.j.oliver)\
**Post date:** [June 6, 2025, 8:41am UTC](https://cylc.discourse.group/t/run-cylc-gui-on-a-different-port/1182/3 "2025-06-06T08:41:08Z")

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All `cylc` commands are self-documenting: `cylc CMD --help`

The `cylc gui` command is a little less obvious, in that it fronts a Jupyter server, but the top level help `cylc gui --help` mentions `cylc gui --help-all`, which shows:

```auto
--ServerApp.port=<Int>
    The port the server will listen on (env: JUPYTER_PORT).

```

So to get it to listen on, say, port 8891, you can do:

```auto
$ cylc gui --port=8891

# or
$ cylc gui --ServerApp.port=8891

# or
$ grep port ~/.cylc/uiserver/jupyter_config,py 
c.ServerApp.port = 8891

```