A Browser for the small internet (Gemini, Gopher, Finger)

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22 hours ago

~mjboa via castor

9 days ago


A graphical client for plain-text protocols written in Rust with GTK. It currently supports the Gemini, Gopher and Finger protocols.







Gemini with some theming:



Castor needs a recent Rust version >= 1.39. Please consider using Rustup if you OS does not package a recent version.


You will need some development libraries:

  • openssl
  • gtk+3
  • gdk-pixbuf
  • pango
  • atk
  • cairo

Build and install

Building on Ubuntu

  • apt install build-essential rustc cargo libgtk-3-dev libgdk-pixbuf2.0-dev libssl-dev
  • make and make install

Building on MacOS

See instructions here

Building on Windows

See instructions here

Changing settings

You can change some settings like initial URL, colors and delimiters for Headers, Lists, Text and Background. Edit ~/.config/castor/settings.toml and add the values you need. These are the keys currently supported, you can use hex codes, plain colors names or even emojis!

start_url = "gemini://gemini.circumlunar.space/capcom"
max_width = 200

h1 = "red"
h2 = "#FF6347"
h3 = "green"
list = "#C71585"
text = "#FF1493"
background = "#FFC0CB"

h1 = ">"
h2 = "))"
h3 = "}}}"
list = "🌼 "

    family = "monospace"
    size = 11
    family = "serif"
    size = 11
    family = "sans"
    size = 16
    style = "normal"
    family = "monospace"
    size = 13
    style = "italic"
    family = "monospace"
    size = 12
    family = "sans"
    size = 11
    style = "oblique"
    family = "sans"
    size = 10
    style = "italic"
    family = "monospace"
    size = 11

Using client certificate

Castor expects your certificates to be placed in your home directory and named after the gemini capsule domain. For example to water your plant on gemini://astrobotany.mozz.us/plant you will need to have astrobotany.mozz.us.crt and astrobotany.mozz.us.key available in your home.

Mailing list

If you have questions, feature requests, bugs or you just want to keep up to date with Castor you can send a message to the mailing list


You can view my current roadmap here


  • Leonora Tindall for the great article on Rust and GTK that helped me bootstrap this project
  • tiwesdaeg for the incredible icon
  • sloum for the great advices
  • the gemini/gopher/finger community for being awesome