Install 4chan X (https://www.4chan-x.net/) and in the settings, under "Advanced", add t...

Install 4chan X (https://www.4chan-x.net/) and in the settings, under "Advanced", add this to the Custom CSS:

⎗

div.post {
    font-family: "DTM Mono";
    font-size: 12pt;
}
div.post span {
    font-weight: normal !important;
}
@font-face {
    font-family: "DTM Mono";
    src: url('https://hushbugger.github.io/dialogue/dtm-mono.woff2') format('woff2');
}

Or for a more narrowly spaced look that's a little less faithful to Undertale:

⎗

div.post {
    font-family: "8bitoperator JVE Regular";
    font-size: 12pt;
}
div.post span {
    font-weight: normal !important;
}
@font-face {
    font-family: "8bitoperator JVE Regular";
    src: url("https://hushbugger.github.io/fonts/8bitoperator_jve.woff") format("woff");
}