Content Negotiation

<div class="viz"><h3>ONE RESOURCE · TWO FORMS</h3><div class="row"><div class="box code" id="accept">Accept: application/json</div><span class="arrow">→</span><div class="box code" id="representation">{ "id": 42 }</div></div><div class="muted" id="content-type">Content-Type: application/json</div></div>

.viz{width:94%;height:88%;max-width:960px;padding:clamp(10px,2vmin,18px);border:1px solid var(--line);border-radius:14px;background:var(--surface);font:600 clamp(12px,1.35vw,16px)/1.35 var(--font-sans,system-ui,sans-serif);display:flex;flex-direction:column;gap:clamp(7px,1.8vmin,13px);overflow:hidden}.viz h3{margin:0;color:var(--accent);font:700 clamp(12px,1.35vw,16px)/1.2 var(--font-sans,system-ui,sans-serif);letter-spacing:.04em}.viz .row{display:flex;align-items:center;justify-content:center;gap:clamp(5px,1.4vmin,12px);flex:1;min-height:0}.viz .box{padding:clamp(5px,1.5vmin,12px);border:1px solid var(--line);border-radius:9px;background:var(--bg);text-align:center}.viz .muted{color:var(--muted)}.viz .accent{color:var(--accent)}.viz .code{font-family:ui-monospace,monospace}.viz .pill{padding:3px 7px;border:1px solid var(--line);border-radius:99px;white-space:nowrap}.viz .active{border-color:var(--accent);background:color-mix(in srgb,var(--accent) 12%,var(--surface))}.viz .arrow{color:var(--accent);font:700 18px ui-monospace,monospace}#accept,#representation{width:41%;overflow-wrap:anywhere}.row{gap:5px}

let json=false;function draw(){json=!json;document.getElementById('accept').textContent=json?'Accept: application/json':'Accept: text/plain';document.getElementById('representation').textContent=json?'{ "id": 42 }':'order 42';document.getElementById('content-type').textContent='Content-Type: '+(json?'application/json':'text/plain')}draw();setInterval(draw,1400)