hugo-theme-relearn/layouts/partials/favicon.html

    {{- $assetBusting := not .Site.Params.disableAssetsBusting }}
    {{- $faviconMatch := false }}
    {{- $svg := dict "ext" "svg" "type" "image/svg+xml" }}
    {{- $png := dict "ext" "png" "type" "image/png" }}
    {{- $ico := dict "ext" "ico" "type" "image/x-icon" }}
    {{- $faviconTypes := slice $svg $png $ico }}
    {{- range $faviconTypes }}
    {{- if and
      (eq $faviconMatch false)
      (or
        (fileExists (printf "/static/images/favicon-light.%s" .ext))
        (fileExists (printf "/static/images/favicon-dark.%s"))
      )
    }}
    {{- $faviconMatch = true }}
    {{/*
      Warning: IE and old browser versions do not support media queries necessary for the light & dark theme option.
      If you have requirements to support IE and/or older browser versions, use one of the other options.
      Reference: https://caniuse.com/css-media-interaction
    */}}
    {{- if (fileExists (printf "/static/images/favicon-light.%s" .ext)) }}
    <link href="{{ printf "images/favicon-light.%s" .ext | relURL }}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="icon" type="{{ .type }}" media="(prefers-color-scheme: light)">
    {{- end }}
    {{- if (fileExists (printf "/static/images/favicon-dark.%s" .ext)) }}
    <link href="{{ printf "images/favicon-dark.%s" .ext | relURL }}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="icon" type="{{ .type }}" media="(prefers-color-scheme: dark)">
    {{- end }}
    {{- end }}
    {{- end }}
    {{- range $faviconTypes }}
    {{- if and
      (eq $faviconMatch false)
      (fileExists (printf "/static/images/favicon.%s" .ext))
    }}
    {{- $faviconMatch = true }}
    <link href="{{ printf "images/favicon.%s" .ext | relURL }}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="icon" type="{{ .type }}">
    {{- end }}
    {{- end }}
    {{- range $faviconTypes }}
    {{- if and
      (eq $faviconMatch false)
      (fileExists (printf "/static/images/logo.%s" .ext))
    }}
    {{- $faviconMatch := true }}
    <link href="{{ printf "images/logo.%s" .ext | relURL }}{{ if $assetBusting }}?{{ now.Unix }}{{ end }}" rel="icon" type="{{ .type }}">
    {{- end }}
    {{- end }}