NOTICES:
I started this project years ago, to solve the "problem" of the Sonarr's blinding white interface. It was a pastime for me, but today it is no longer so, I am unmotivated to update it and keep up with the continuous changes of Sonarr, Radarr and Lidarr, so I decided to archive this project.

Over the years other excellent alternative themes have been born, take a look at:
gilbN/theme.park
Archmonger/Blackberry-Themes

A darker theme for Sonarr, Radarr & Lidarr

Note:

• Darkerr v3 works only on Sonarr v3 and Lidarr (soon also Radarr v1)
• If you use an old versions (Sonarr v2 and Radarr v0), take a look at Darkerr v2

• Installation
  • Server-side installation (for, eg, "http://localhost/sonarr")
  • Browser-side installation (for, eg, "http://localhost/8989")
• Screenshots

• Server-side installation

  • Add these lines to your Sonarr/Radarr/Lidarr location blocks in nginx.conf:

    proxy_set_header Accept-Encoding "";
    sub_filter
        '</head>'
        '<link rel="stylesheet" type="text/css" href="//raw.githack.com/iFelix18/Darkerr/develop/darkerr.css">
         </head>';
    sub_filter_once on;

  • Restart nginx.
  • Done! From now on it will automatically update.

• Browser-side installation

  • Download this add-on for your browser
    • Stylus: Firefox, Chrome, or Opera.
  • Click here to install directly with Stylus.
  • Done! From now on it will automatically update.

  You do not use the default ports (8989 for Sonarr, 7878 for Radarr and 8686 for Lidarr)?

  Answer

  If so, just change this string via Stylus:

      [...]
      @updateURL      https://raw.githubusercontent.com/iFelix18/Darkerr/develop/darkerr.user.css
      @license        CC-BY-SA-4.0
      ==/UserStyle== */
  -   @-moz-document regexp("((http(s?)):\\/\\/)?[-A-Za-z0-9+&@#/%?=~_|!:,.;]+(8989|7878|8686)+(.*)") {
  +   @-moz-document regexp("((http(s?)):\\/\\/)?[-A-Za-z0-9+&@#/%?=~_|!:,.;]+(your custom Sonarr port|your custom Radarr port|your custom Lidarr port)+(.*)") {
      /* --- VERSION --- */
      @media (min-width: 768px) {
          .About-descriptionList-1_gea.DescriptionList-descriptionList-2MSh3 > span:nth-child(1) > .DescriptionListItemTitle-title-EA460:after {
      [...]

  (Note: for each update of Darkerr, this change must be done again)