Tabs — switch between panels

Tab navigation that switches content panels. Pure CSS using :target or radio inputs (no JS needed for basic tabs).

style.css v3.1

style.css — the CSS rules

/* Tab navigation */
.tabs {
  border-bottom: 2px solid #e0e0e0;
  display: flex;
  gap: 0.3rem;
  margin-bottom: 1.5rem;
}

.tabs .tab {
  padding: 0.7rem 1.2rem;
  border: none;
  background: none;
  font-size: 0.92rem;
  color: #666;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  margin-bottom: -2px;
  transition: all 0.15s;
  font-family: inherit;
}

.tabs .tab:hover {
  color: #333;
  background: #f5f5f5;
}

.tabs .tab.active {
  color: #a0c000;
  border-bottom-color: #a0c000;
  font-weight: 600;
}

/* Tab content panels */
.tab-panel {
  display: none;
  padding: 1rem 0;
  line-height: 1.6;
}

.tab-panel.active {
  display: block;
}

index.html — the HTML structure (what the CSS targets)

<div class="tabs">
  <button class="tab active" onclick="document.querySelectorAll('.tab').forEach(t=>t.classList.remove('active'));document.querySelectorAll('.tab-panel').forEach(p=>p.classList.remove('active'));this.classList.add('active');document.getElementById('p1').classList.add('active')">Overview</button>
  <button class="tab" onclick="document.querySelectorAll('.tab').forEach(t=>t.classList.remove('active'));document.querySelectorAll('.tab-panel').forEach(p=>p.classList.remove('active'));this.classList.add('active');document.getElementById('p2').classList.add('active')">Metrics</button>
  <button class="tab" onclick="document.querySelectorAll('.tab').forEach(t=>t.classList.remove('active'));document.querySelectorAll('.tab-panel').forEach(p=>p.classList.remove('active'));this.classList.add('active');document.getElementById('p3').classList.add('active')">Code</button>
</div>
<div class="tab-panel active" id="p1">
  <h3>Overview</h3>
  <p>RandomForest classifier trained on the Iris dataset. 100 trees, max depth 10.</p>
</div>
<div class="tab-panel" id="p2">
  <h3>Metrics</h3>
  <p>Accuracy: 94.2% | Precision: 91.8% | Recall: 89.3% | F1: 90.5%</p>
</div>
<div class="tab-panel" id="p3">
  <h3>Code</h3>
  <p>from sklearn.ensemble import RandomForestClassifier</p>
  <p>clf = RandomForestClassifier(n_estimators=100, max_depth=10)</p>
  <p>clf.fit(X_train, y_train)</p>
</div>

Live preview updates as you type

🧠 How it works

The .tabs container has a bottom border — the 'tab bar'. Each .tab is a <button> with: transparent background, bottom border that's invisible until active. margin-bottom: -2px — the tab's bottom border overlaps the tab bar's border (so the active tab 'connects'). Active tab: colored bottom border + colored text + bold. Tab panels: display: none by default, display: block when .active. The onclick JS just toggles .active classes — the CSS handles the visual switching. In a real app, you'd use addEventListener instead of inline onclick, but the CSS is the same.

✏️ Try these changes

Change border-bottom: 3px to 5px on .tab.active
→ thicker active indicator
Change the active color from #a0c000 to #58a6ff
→ tabs become blue
Change .tab font-size from 0.92rem to 1.1rem
→ bigger tab labels
Add border-radius: 6px 6px 0 0 to .tab
→ tabs get rounded top corners

← Previous lab

Footer — bottom of the page

Next lab →

Full dashboard layout — sidebar + KPIs + charts + table