diff --git a/docs/embed.md b/docs/embed.md
index 9b190eda..10ae6711 100644
--- a/docs/embed.md
+++ b/docs/embed.md
@@ -1,3 +1,23 @@
 You can embed the URL using an iframe in your website.
 
 Optionally append `?readonly` to make the editor read-only.
+
+Use `show` with `widths` to control which panes are visible and how much
+horizontal space each pane gets:
+
+```html
+<iframe src="https://codepan.net/?readonly&show=js,console,output&widths=25,25,50"></iframe>
+```
+
+The `widths` value is a comma-separated list that matches the visible pane
+order: HTML, CSS, JS, Console, Output. Values are relative, so `1,1,2` and
+`25,25,50` produce the same layout.
+
+For order-independent embeds, use named pane widths:
+
+```html
+<iframe src="https://codepan.net/?readonly&show=js,console,output&widths=js:25,console:25,output:50"></iframe>
+```
+
+If `widths` is missing, invalid, or does not cover every visible pane, CodePan
+keeps the default equal-width layout.
diff --git a/package.json b/package.json
index 7ba66a1b..f1181a8e 100644
--- a/package.json
+++ b/package.json
@@ -10,6 +10,7 @@
   "repository": {},
   "scripts": {
     "test": "npm run lint",
+    "test:pan-widths": "node test/pan-widths.js",
     "lint": "xo",
     "dev": "poi",
     "build": "poi build",
diff --git a/src/components/ConsolePan.vue b/src/components/ConsolePan.vue
index d9df33b3..3161be1b 100644
--- a/src/components/ConsolePan.vue
+++ b/src/components/ConsolePan.vue
@@ -56,8 +56,11 @@
       visiblePans: {
         immediate: true,
         handler(val) {
-          this.style = panPosition(val, 'console')
+          this.style = panPosition(val, 'console', this.panWidths)
         }
+      },
+      panWidths(val) {
+        this.style = panPosition(this.visiblePans, 'console', val)
       }
     },
     mounted() {
@@ -69,7 +72,7 @@
       })
     },
     computed: {
-      ...mapState(['logs', 'visiblePans', 'activePan']),
+      ...mapState(['logs', 'visiblePans', 'activePan', 'panWidths']),
       enableResizer() {
         return hasNextPan(this.visiblePans, 'console')
       },
diff --git a/src/components/OutputPan.vue b/src/components/OutputPan.vue
index 16084e3b..038dbbcf 100644
--- a/src/components/OutputPan.vue
+++ b/src/components/OutputPan.vue
@@ -76,8 +76,11 @@ export default {
     visiblePans: {
       immediate: true,
       handler(val) {
-        this.style = panPosition(val, 'output')
+        this.style = panPosition(val, 'output', this.panWidths)
       }
+    },
+    panWidths(val) {
+      this.style = panPosition(this.visiblePans, 'output', val)
     }
   },
   computed: {
@@ -86,6 +89,7 @@ export default {
       'css',
       'html',
       'visiblePans',
+      'panWidths',
       'activePan',
       'githubToken',
       'iframeStatus'
diff --git a/src/store/index.js b/src/store/index.js
index dd52913f..359dcf26 100644
--- a/src/store/index.js
+++ b/src/store/index.js
@@ -17,6 +17,7 @@ import progress from 'nprogress'
 import api from '@/utils/github-api'
 import req from 'reqjs'
 import Event from '@/utils/event'
+import { parsePanWidths } from '@/utils/pan-widths'
 
 Vue.use(Vuex)
 
@@ -75,7 +76,9 @@ const store = new Vuex.Store({
     userMeta: JSON.parse(localStorage.getItem('codepan:user-meta')) || {},
     editorStatus: 'saved',
     iframeStatus: null,
-    transforming: false
+    transforming: false,
+    panWidthsQuery: null,
+    panWidths: null
   },
   mutations: {
     UPDATE_CODE(state, { type, code }) {
@@ -102,6 +105,11 @@ const store = new Vuex.Store({
     },
     SHOW_PANS(state, pans) {
       state.visiblePans = sortPans(pans)
+      state.panWidths = parsePanWidths(state.panWidthsQuery, state.visiblePans)
+    },
+    SET_PAN_WIDTHS(state, value) {
+      state.panWidthsQuery = value
+      state.panWidths = parsePanWidths(value, state.visiblePans)
     },
     ACTIVE_PAN(state, pan) {
       state.activePan = pan
@@ -150,6 +158,9 @@ const store = new Vuex.Store({
     showPans({ commit }, pans) {
       commit('SHOW_PANS', pans)
     },
+    setPanWidths({ commit }, value) {
+      commit('SET_PAN_WIDTHS', value)
+    },
     async updateTransformer({ commit }, { type, transformer }) {
       if (
         transformer === 'babel' ||
diff --git a/src/utils/create-pan.js b/src/utils/create-pan.js
index fc74fdad..19f5b9d8 100644
--- a/src/utils/create-pan.js
+++ b/src/utils/create-pan.js
@@ -17,7 +17,7 @@ export default ({ name, editor, components } = {}) => {
       }
     },
     computed: {
-      ...mapState([name, 'visiblePans', 'activePan', 'autoRun']),
+      ...mapState([name, 'visiblePans', 'activePan', 'autoRun', 'panWidths']),
       ...mapState({
         isVisible: state => state.visiblePans.indexOf(name) !== -1
       }),
@@ -38,9 +38,12 @@ export default ({ name, editor, components } = {}) => {
       visiblePans: {
         immediate: true,
         handler(val) {
-          this.style = panPosition(val, name)
+          this.style = panPosition(val, name, this.panWidths)
         }
       },
+      panWidths(val) {
+        this.style = panPosition(this.visiblePans, name, val)
+      },
       [`${name}.transformer`](val) {
         const mode = getEditorModeByTransfomer(val)
         this.editor.setOption('mode', mode)
diff --git a/src/utils/pan-position.js b/src/utils/pan-position.js
index 50ab4257..db1399de 100644
--- a/src/utils/pan-position.js
+++ b/src/utils/pan-position.js
@@ -1,4 +1,12 @@
-export default (pans, pan) => {
+import { getPanPosition } from '@/utils/pan-widths'
+
+export default (pans, pan, widths) => {
+  const customPosition = getPanPosition(pans, pan, widths)
+
+  if (customPosition) {
+    return customPosition
+  }
+
   const panWidth = 100 / pans.length
   const pansCount = matchedPans => {
     return pans.filter(p => {
diff --git a/src/utils/pan-widths.js b/src/utils/pan-widths.js
new file mode 100644
index 00000000..1bda55a5
--- /dev/null
+++ b/src/utils/pan-widths.js
@@ -0,0 +1,115 @@
+const panNames = ['html', 'css', 'js', 'console', 'output']
+
+const normalizeQueryValue = value => {
+  if (Array.isArray(value)) {
+    return value[0]
+  }
+
+  return value
+}
+
+const parseWidth = value => {
+  const parsed = Number(String(value).trim().replace(/%$/, ''))
+
+  return Number.isFinite(parsed) && parsed > 0 ? parsed : null
+}
+
+const normalizeWidths = widths => {
+  const total = widths.reduce((sum, width) => sum + width, 0)
+
+  if (total <= 0) {
+    return null
+  }
+
+  return widths.map(width => width / total * 100)
+}
+
+const parseEntry = entry => {
+  const separator = entry.indexOf(':')
+
+  if (separator === -1) {
+    return {
+      width: parseWidth(entry)
+    }
+  }
+
+  return {
+    pan: entry.slice(0, separator).trim(),
+    width: parseWidth(entry.slice(separator + 1))
+  }
+}
+
+const parseEntries = value => {
+  return String(value)
+    .split(',')
+    .map(entry => entry.trim())
+    .filter(Boolean)
+    .map(parseEntry)
+}
+
+const parseNamedWidths = (entries, visiblePans) => {
+  const widthsByPan = {}
+
+  for (const { pan, width } of entries) {
+    if (!pan || panNames.indexOf(pan) === -1 || width === null || widthsByPan[pan]) {
+      return null
+    }
+
+    widthsByPan[pan] = width
+  }
+
+  const widths = visiblePans.map(pan => widthsByPan[pan])
+
+  if (Object.keys(widthsByPan).length !== visiblePans.length || widths.some(width => width === undefined)) {
+    return null
+  }
+
+  return normalizeWidths(widths)
+}
+
+const parseOrderedWidths = (entries, visiblePans) => {
+  if (entries.length !== visiblePans.length || entries.some(({ pan, width }) => pan || width === null)) {
+    return null
+  }
+
+  return normalizeWidths(entries.map(({ width }) => width))
+}
+
+const formatPercent = value => `${Number(value.toFixed(6))}%`
+
+export const parsePanWidths = (value, visiblePans) => {
+  value = normalizeQueryValue(value)
+
+  if (!value || !Array.isArray(visiblePans) || visiblePans.length === 0) {
+    return null
+  }
+
+  const entries = parseEntries(value)
+
+  if (entries.length === 0) {
+    return null
+  }
+
+  const hasNamedEntries = entries.some(({ pan }) => pan)
+
+  return hasNamedEntries ?
+    parseNamedWidths(entries, visiblePans) :
+    parseOrderedWidths(entries, visiblePans)
+}
+
+export const getPanPosition = (visiblePans, pan, widths) => {
+  const index = visiblePans.indexOf(pan)
+
+  if (!widths || index === -1 || widths.length !== visiblePans.length) {
+    return null
+  }
+
+  const left = widths.slice(0, index).reduce((sum, width) => sum + width, 0)
+  const width = widths[index]
+  const right = Math.max(0, 100 - left - width)
+
+  return {
+    left: formatPercent(left),
+    right: formatPercent(right)
+  }
+}
diff --git a/src/views/EditorPage.vue b/src/views/EditorPage.vue
index 058100bd..268aba0e 100644
--- a/src/views/EditorPage.vue
+++ b/src/views/EditorPage.vue
@@ -120,6 +120,12 @@ export default {
         }
       },
       immediate: true
+    },
+    '$route.query.widths': {
+      handler(next) {
+        this.setPanWidths(next)
+      },
+      immediate: true
     }
   },
   mounted() {
@@ -154,7 +160,7 @@ export default {
     })
   },
   methods: {
-    ...mapActions(['setBoilerplate', 'setGist', 'showPans', 'setAutoRun']),
+    ...mapActions(['setBoilerplate', 'setGist', 'showPans', 'setAutoRun', 'setPanWidths']),
     isVisible(pan) {
       return this.visiblePans.indexOf(pan) !== -1
     },
diff --git a/test/pan-widths.js b/test/pan-widths.js
new file mode 100644
index 00000000..87a393eb
--- /dev/null
+++ b/test/pan-widths.js
@@ -0,0 +1,39 @@
+require('babel-register')({
+  presets: [['env', { modules: 'commonjs' }]],
+  ignore: /node_modules/
+})
+
+const assert = require('assert')
+const { parsePanWidths, getPanPosition } = require('../src/utils/pan-widths')
+
+const visiblePans = ['js', 'console', 'output']
+
+assert.deepStrictEqual(parsePanWidths('25,25,50', visiblePans), [25, 25, 50])
+assert.deepStrictEqual(parsePanWidths('1,1,2', visiblePans), [25, 25, 50])
+assert.deepStrictEqual(parsePanWidths('25%, 25%, 50%', visiblePans), [25, 25, 50])
+assert.deepStrictEqual(parsePanWidths('output:50,js:25,console:25', visiblePans), [25, 25, 50])
+assert.deepStrictEqual(parsePanWidths('js:1,console:1,output:2', visiblePans), [25, 25, 50])
+assert.deepStrictEqual(parsePanWidths(['25,25,50'], visiblePans), [25, 25, 50])
+
+assert.strictEqual(parsePanWidths('', visiblePans), null)
+assert.strictEqual(parsePanWidths('25,25', visiblePans), null)
+assert.strictEqual(parsePanWidths('25,nope,50', visiblePans), null)
+assert.strictEqual(parsePanWidths('25,-1,50', visiblePans), null)
+assert.strictEqual(parsePanWidths('js:25,output:75', visiblePans), null)
+assert.strictEqual(parsePanWidths('js:25,console:25,output:0', visiblePans), null)
+assert.strictEqual(parsePanWidths('js:25,console:25,output:25,html:25', visiblePans), null)
+assert.strictEqual(parsePanWidths('missing:25,console:25,output:50', visiblePans), null)
+
+assert.deepStrictEqual(
+  getPanPosition(visiblePans, 'js', [25, 25, 50]),
+  { left: '0%', right: '75%' }
+)
+assert.deepStrictEqual(
+  getPanPosition(visiblePans, 'console', [25, 25, 50]),
+  { left: '25%', right: '50%' }
+)
+assert.deepStrictEqual(
+  getPanPosition(visiblePans, 'output', [25, 25, 50]),
+  { left: '50%', right: '0%' }
+)
+assert.strictEqual(getPanPosition(['js', 'output'], 'output', [25, 25, 50]), null)