diff --git a/README.md b/README.md
index 6d1ac08..688cef7 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,8 @@
 
 Windows desktop client for the Metatron.Drive private file workspace.
 
+Users sign in once, can hold multiple approved organization memberships, submit additional join-code requests, and switch the active organization locally.
+
 ## Stack
 
 - Electron
diff --git a/src/App.jsx b/src/App.jsx
index cfb69f1..4feab12 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react'
+import { useCallback, useEffect, useState } from 'react'
 import { api } from './lib/api.js'
 import Splash from './components/Splash.jsx'
 import AuthScreen from './components/AuthScreen.jsx'
@@ -7,6 +7,16 @@ import DriveApp from './components/DriveApp.jsx'
 export default function App() {
   const [status, setStatus] = useState('loading')
   const [user, setUser] = useState(null)
+  const [organizationId, setOrganizationId] = useState(() => localStorage.getItem('metatron.drive-organization'))
+
+  const applyProfile = useCallback((profile) => {
+    const approved = (profile.memberships || []).filter((item) => item.status === 'APPROVED' && item.organization?.status === 'ACTIVE')
+    const selected = approved.find((item) => item.organization.id === organizationId) || approved[0]
+    if (!selected) throw new Error('No approved organization membership is available.')
+    localStorage.setItem('metatron.drive-organization', selected.organization.id)
+    setOrganizationId(selected.organization.id)
+    setUser(profile)
+  }, [organizationId])
 
   useEffect(() => {
     let active = true
@@ -16,14 +26,14 @@ export default function App() {
       if (!token) return setStatus('signedOut')
       try {
         const profile = await api.me()
-        if (active) { setUser(profile); setStatus('signedIn') }
+        if (active) { applyProfile(profile); setStatus('signedIn') }
       } catch {
         await window.desktop.session.clear()
         if (active) setStatus('signedOut')
       }
     })
     return () => { active = false }
-  }, [])
+  }, [applyProfile])
 
   async function logout() {
     await window.desktop.session.clear()
@@ -31,7 +41,17 @@ export default function App() {
     setStatus('signedOut')
   }
 
+  async function refreshUser() {
+    const profile = await api.me()
+    applyProfile(profile)
+  }
+
+  function selectOrganization(id) {
+    localStorage.setItem('metatron.drive-organization', id)
+    setOrganizationId(id)
+  }
+
   if (status === 'loading') return <Splash />
-  if (status === 'signedOut') return <AuthScreen onAuthenticated={(profile) => { setUser(profile); setStatus('signedIn') }} />
-  return <DriveApp user={user} onLogout={logout} />
+  if (status === 'signedOut') return <AuthScreen onAuthenticated={(profile) => { applyProfile(profile); setStatus('signedIn') }} />
+  return <DriveApp key={organizationId} user={user} organizationId={organizationId} onSelectOrganization={selectOrganization} onRefreshUser={refreshUser} onLogout={logout} />
 }
diff --git a/src/components/AuthScreen.jsx b/src/components/AuthScreen.jsx
index dddc4fe..19e8b62 100644
--- a/src/components/AuthScreen.jsx
+++ b/src/components/AuthScreen.jsx
@@ -2,7 +2,7 @@ import { useState } from 'react'
 import { ArrowLeft, Cloud, Eye, EyeOff, LockKeyhole, Mail, Phone, User, UserRound } from 'lucide-react'
 import { api, errorMessage } from '../lib/api.js'
 
-const emptyRegister = { name: '', username: '', email: '', phone: '', password: '' }
+const emptyRegister = { organizationCode: '', name: '', username: '', email: '', phone: '', password: '' }
 
 export default function AuthScreen({ onAuthenticated }) {
   const [mode, setMode] = useState('login')
@@ -11,12 +11,14 @@ export default function AuthScreen({ onAuthenticated }) {
   const [hidden, setHidden] = useState(true)
   const [busy, setBusy] = useState(false)
   const [error, setError] = useState('')
+  const [notice, setNotice] = useState('')
 
   async function submitLogin(event) {
     event.preventDefault()
     if (login.username.trim().length < 3 || !login.password) return setError('Enter your username and password.')
     setBusy(true)
     setError('')
+    setNotice('')
     try {
       const result = await api.login(login.username.trim(), login.password)
       await window.desktop.session.write(result.token)
@@ -31,6 +33,7 @@ export default function AuthScreen({ onAuthenticated }) {
   async function submitRegister(event) {
     event.preventDefault()
     const username = register.username.trim().toLowerCase()
+    if (register.organizationCode.trim().length < 4) return setError('Enter your organization code.')
     if (register.name.trim().length < 2) return setError('Enter your full name.')
     if (!/^[a-z0-9._-]{3,30}$/.test(username)) return setError('Enter a valid username.')
     if (!/^.+@.+\..+$/.test(register.email.trim())) return setError('Enter a valid email address.')
@@ -40,6 +43,7 @@ export default function AuthScreen({ onAuthenticated }) {
     setError('')
     try {
       const result = await api.register({
+        organizationCode: register.organizationCode.trim().toUpperCase(),
         name: register.name.trim(),
         username,
         email: register.email.trim().toLowerCase(),
@@ -48,8 +52,8 @@ export default function AuthScreen({ onAuthenticated }) {
         gender: 'Prefer not to say',
         password: register.password,
       })
-      await window.desktop.session.write(result.token)
-      onAuthenticated(result.user)
+      setNotice(result.message)
+      setRegister(emptyRegister)
     } catch (requestError) {
       setError(errorMessage(requestError))
     } finally {
@@ -85,7 +89,7 @@ export default function AuthScreen({ onAuthenticated }) {
               <Field icon={UserRound} label="Username" value={login.username} onChange={(value) => setLogin({ ...login, username: value })} autoFocus />
               <PasswordField value={login.password} onChange={(value) => setLogin({ ...login, password: value })} hidden={hidden} setHidden={setHidden} />
             </div>
-            {error && <ErrorBox message={error} />}
+            {error && <ErrorBox message={error} />}{notice && <NoticeBox message={notice} />}
             <button className="btn-primary mt-6 w-full" disabled={busy}>{busy ? <Spinner /> : 'Sign in'}</button>
             <button type="button" className="mt-5 w-full text-sm font-bold text-blue-600 hover:text-blue-700" onClick={() => { setError(''); setMode('register') }}>New to the family? Create an account</button>
           </form>
@@ -95,13 +99,14 @@ export default function AuthScreen({ onAuthenticated }) {
             <h2 className="text-3xl font-black text-slate-900">Join the digital family</h2>
             <p className="mt-2 text-slate-500">We create your private Google Drive folder automatically.</p>
             <div className="mt-7 grid grid-cols-2 gap-4">
-              <div className="col-span-2"><Field icon={User} label="Full name" value={register.name} onChange={(value) => setRegister({ ...register, name: value })} autoFocus /></div>
+              <div className="col-span-2"><Field icon={Cloud} label="Organization code" value={register.organizationCode} onChange={(value) => setRegister({ ...register, organizationCode: value.toUpperCase() })} autoFocus /></div>
+              <div className="col-span-2"><Field icon={User} label="Full name" value={register.name} onChange={(value) => setRegister({ ...register, name: value })} /></div>
               <Field icon={UserRound} label="Username" value={register.username} onChange={(value) => setRegister({ ...register, username: value })} />
               <Field icon={Mail} type="email" label="Email address" value={register.email} onChange={(value) => setRegister({ ...register, email: value })} />
               <div className="col-span-2"><Field icon={Phone} label="Phone number (optional)" value={register.phone} onChange={(value) => setRegister({ ...register, phone: value })} /></div>
               <div className="col-span-2"><PasswordField value={register.password} onChange={(value) => setRegister({ ...register, password: value })} hidden={hidden} setHidden={setHidden} /></div>
             </div>
-            {error && <ErrorBox message={error} />}
+            {error && <ErrorBox message={error} />}{notice && <NoticeBox message={notice} />}
             <button className="btn-primary mt-6 w-full" disabled={busy}>{busy ? <Spinner /> : 'Create Metatron.Drive'}</button>
           </form>
         )}
@@ -122,6 +127,10 @@ function ErrorBox({ message }) {
   return <div className="mt-5 rounded-xl border border-red-200 bg-red-50 px-4 py-3 text-sm font-medium text-red-700">{message}</div>
 }
 
+function NoticeBox({ message }) {
+  return <div className="mt-5 rounded-xl border border-emerald-200 bg-emerald-50 px-4 py-3 text-sm font-medium text-emerald-700">{message}</div>
+}
+
 function Spinner() {
   return <span className="h-5 w-5 animate-spin rounded-full border-2 border-white/30 border-t-white" />
 }
diff --git a/src/components/DriveApp.jsx b/src/components/DriveApp.jsx
index 04a25dc..b4e03c6 100644
--- a/src/components/DriveApp.jsx
+++ b/src/components/DriveApp.jsx
@@ -11,7 +11,7 @@ import { useUploads } from '../hooks/useUploads.js'
 import Modal from './Modal.jsx'
 import UploadHistory from './UploadHistory.jsx'
 
-export default function DriveApp({ user, onLogout }) {
+export default function DriveApp({ user, organizationId, onSelectOrganization, onRefreshUser, onLogout }) {
   const [path, setPath] = useState([])
   const [folders, setFolders] = useState([])
   const [files, setFiles] = useState([])
@@ -23,6 +23,8 @@ export default function DriveApp({ user, onLogout }) {
   const [toast, setToast] = useState(null)
   const inputRef = useRef(null)
   const folderId = path.at(-1)?.id || null
+  const memberships = (user.memberships || []).filter((item) => item.status === 'APPROVED' && item.organization?.status === 'ACTIVE')
+  const selectedMembership = memberships.find((item) => item.organization.id === organizationId) || memberships[0]
 
   const load = useCallback(async () => {
     setLoading(true)
@@ -51,7 +53,7 @@ export default function DriveApp({ user, onLogout }) {
   const onUploadComplete = useCallback((destinationId) => {
     if ((destinationId || null) === folderId) load()
   }, [folderId, load])
-  const uploadState = useUploads(onUploadComplete)
+  const uploadState = useUploads(onUploadComplete, organizationId)
 
   async function createFolder(name) {
     try {
@@ -110,13 +112,13 @@ export default function DriveApp({ user, onLogout }) {
 
   return (
     <main className="flex h-screen bg-[#f6f8fc]">
-      <Sidebar user={user} view={view} setView={setView} activeUploads={uploadState.active.length} onProfile={() => setModal('profile')} />
+      <Sidebar user={user} memberships={memberships} organizationId={organizationId} onSelectOrganization={onSelectOrganization} view={view} setView={setView} activeUploads={uploadState.active.length} onJoin={() => setModal('join')} onProfile={() => setModal('profile')} />
       <section className="flex min-w-0 flex-1 flex-col">
         <header className="flex h-[82px] shrink-0 items-center gap-5 border-b border-slate-200 bg-white px-7">
           {view === 'drive' && path.length > 0 && <button className="icon-btn" onClick={() => setPath((current) => current.slice(0, -1))}><ArrowLeft size={21} /></button>}
           <div className="min-w-0 flex-1">
-            <h1 className="truncate text-xl font-black text-slate-900">{view === 'history' ? 'Upload history' : path.at(-1)?.name || 'Metatron.Drive'}</h1>
-            <p className="mt-0.5 text-xs text-slate-500">{view === 'history' ? 'Track every desktop upload' : `Hello, ${user.name.split(' ')[0]}`}</p>
+            <h1 className="truncate text-xl font-black text-slate-900">{view === 'history' ? 'Upload history' : path.at(-1)?.name || selectedMembership?.organization.name || 'Metatron.Drive'}</h1>
+            <p className="mt-0.5 text-xs text-slate-500">{view === 'history' ? `Uploads for ${selectedMembership?.organization.name}` : `Hello, ${user.name.split(' ')[0]} · ${selectedMembership?.organization.code}`}</p>
           </div>
           {view === 'drive' && <>
             <label className="relative w-72"><Search className="absolute left-3.5 top-2.5 text-slate-400" size={18} /><input className="field py-2 pl-10" placeholder="Search this folder" value={search} onChange={(event) => setSearch(event.target.value)} /></label>
@@ -155,19 +157,23 @@ export default function DriveApp({ user, onLogout }) {
       {uploadState.active.length > 0 && <ActiveUploadBar items={uploadState.active} onOpen={() => setView('history')} onCancel={uploadState.cancel} />}
       {toast && <Toast toast={toast} />}
       {modal === 'folder' && <NewFolderModal onClose={() => setModal(null)} onCreate={createFolder} />}
+      {modal === 'join' && <JoinOrganizationModal onClose={() => setModal(null)} onJoined={async (message) => { await onRefreshUser(); setModal(null); setToast({ type: 'success', message }) }} />}
       {modal === 'profile' && <ProfileModal user={user} onClose={() => setModal(null)} onLogout={onLogout} onDeleted={onLogout} setToast={setToast} />}
       {modal?.type === 'preview' && <PreviewModal item={modal.item} onClose={() => setModal(null)} onDownload={() => downloadFile(modal.item)} />}
     </main>
   )
 }
 
-function Sidebar({ user, view, setView, activeUploads, onProfile }) {
+function Sidebar({ user, memberships, organizationId, onSelectOrganization, view, setView, activeUploads, onJoin, onProfile }) {
   return <aside className="flex w-64 shrink-0 flex-col border-r border-slate-200 bg-white px-4 py-5">
     <div className="flex items-center gap-3 px-3 text-lg font-black"><span className="flex h-10 w-10 items-center justify-center rounded-2xl bg-blue-600 text-white"><Cloud size={23} fill="currentColor" /></span>Metatron.Drive</div>
     <nav className="mt-9 space-y-1">
       <NavButton active={view === 'drive'} icon={HardDrive} label="My Drive" onClick={() => setView('drive')} />
       <NavButton active={view === 'history'} icon={History} label="Upload history" badge={activeUploads || null} onClick={() => setView('history')} />
     </nav>
+    <label className="mt-7 px-3 text-[10px] font-black uppercase tracking-wider text-slate-400">Organization</label>
+    <select className="field mt-2 py-2 text-sm font-bold" value={organizationId || ''} onChange={(event) => onSelectOrganization(event.target.value)}>{memberships.map((item) => <option key={item.organization.id} value={item.organization.id}>{item.organization.name}</option>)}</select>
+    <button className="mt-2 px-3 text-left text-xs font-bold text-blue-600" onClick={onJoin}>+ Join another organization</button>
     <div className="mt-8 rounded-2xl bg-[#101d42] p-4 text-white">
       <ShieldCheck className="text-emerald-300" size={23} />
       <p className="mt-3 text-sm font-bold">Private workspace</p>
@@ -250,6 +256,25 @@ function NewFolderModal({ onClose, onCreate }) {
   return <Modal title="New folder" onClose={onClose}><form onSubmit={(event) => { event.preventDefault(); if (name.trim()) onCreate(name.trim()) }}><label className="text-sm font-bold text-slate-600">Folder name</label><input className="field mt-2" value={name} onChange={(event) => setName(event.target.value)} autoFocus maxLength={100} /><div className="mt-6 flex justify-end gap-3"><button type="button" className="btn-secondary" onClick={onClose}>Cancel</button><button className="btn-primary py-2.5" disabled={!name.trim()}><FolderPlus size={18} /> Create folder</button></div></form></Modal>
 }
 
+function JoinOrganizationModal({ onClose, onJoined }) {
+  const [code, setCode] = useState('')
+  const [organization, setOrganization] = useState(null)
+  const [busy, setBusy] = useState(false)
+  const [error, setError] = useState('')
+  async function find(event) {
+    event.preventDefault(); setBusy(true); setError('')
+    try { setOrganization(await api.lookupOrganization(code.trim().toUpperCase())) }
+    catch (requestError) { setError(errorMessage(requestError)); setOrganization(null) }
+    finally { setBusy(false) }
+  }
+  async function join() {
+    setBusy(true); setError('')
+    try { const result = await api.joinOrganization(code.trim().toUpperCase()); await onJoined(result.message) }
+    catch (requestError) { setError(errorMessage(requestError)); setBusy(false) }
+  }
+  return <Modal title="Join an organization" onClose={onClose}><form onSubmit={find}><label className="text-sm font-bold text-slate-600">Organization code</label><input className="field mt-2 uppercase" value={code} onChange={(event) => { setCode(event.target.value.toUpperCase()); setOrganization(null) }} autoFocus /><button className="btn-secondary mt-3 w-full" disabled={busy || code.trim().length < 4}>{busy ? 'Checking…' : 'Find organization'}</button></form>{organization && <div className="mt-5 rounded-xl border border-blue-200 bg-blue-50 p-4"><p className="font-black text-slate-800">{organization.name}</p><p className="mt-1 text-xs text-slate-500">Code: {organization.code}</p><button className="btn-primary mt-4 w-full" disabled={busy} onClick={join}>Request to join</button></div>}{error && <p className="mt-4 text-sm font-bold text-red-600">{error}</p>}</Modal>
+}
+
 function ProfileModal({ user, onClose, onLogout, onDeleted, setToast }) {
   const [deleting, setDeleting] = useState(false)
   const [password, setPassword] = useState('')
diff --git a/src/hooks/useUploads.js b/src/hooks/useUploads.js
index 4895fbe..b58c2f9 100644
--- a/src/hooks/useUploads.js
+++ b/src/hooks/useUploads.js
@@ -12,7 +12,7 @@ function readHistory() {
   }
 }
 
-export function useUploads(onComplete) {
+export function useUploads(onComplete, organizationId) {
   const [uploads, setUploadsState] = useState(readHistory)
   const fileRefs = useRef(new Map())
   const abortRefs = useRef(new Map())
@@ -63,6 +63,7 @@ export function useUploads(onComplete) {
         size: file.size,
         type: file.type || 'application/octet-stream',
         folderId: folderId || null,
+        organizationId,
         createdAt: new Date().toISOString(),
         status: 'queued',
         progress: 0,
@@ -72,7 +73,7 @@ export function useUploads(onComplete) {
       setUploads((current) => [entry, ...current])
       run(entry, file)
     }
-  }, [run, setUploads])
+  }, [organizationId, run, setUploads])
 
   const cancel = useCallback((id) => abortRefs.current.get(id)?.abort(), [])
 
@@ -97,6 +98,7 @@ export function useUploads(onComplete) {
     setUploads((current) => current.filter((item) => !finalStatuses.has(item.status)))
   }, [setUploads])
 
-  const active = useMemo(() => uploads.filter((item) => !finalStatuses.has(item.status)), [uploads])
-  return { uploads, active, enqueue, cancel, retry, remove, clearFinished }
+  const visibleUploads = useMemo(() => uploads.filter((item) => !item.organizationId || item.organizationId === organizationId), [organizationId, uploads])
+  const active = useMemo(() => visibleUploads.filter((item) => !finalStatuses.has(item.status)), [visibleUploads])
+  return { uploads: visibleUploads, active, enqueue, cancel, retry, remove, clearFinished }
 }
diff --git a/src/lib/api.js b/src/lib/api.js
index d743ff9..1870cc2 100644
--- a/src/lib/api.js
+++ b/src/lib/api.js
@@ -10,6 +10,8 @@ const client = axios.create({
 client.interceptors.request.use(async (config) => {
   const token = await window.desktop.session.read()
   if (token) config.headers.Authorization = `Bearer ${token}`
+  const organizationId = localStorage.getItem('metatron.drive-organization')
+  if (organizationId) config.headers['X-Organization-Id'] = organizationId
   return config
 })
 
@@ -24,6 +26,12 @@ export const api = {
   async register(input) {
     return (await client.post('/auth/register', input)).data
   },
+  async joinOrganization(organizationCode) {
+    return (await client.post('/auth/join', { organizationCode })).data
+  },
+  async lookupOrganization(code) {
+    return (await client.get(`/organizations/lookup/${encodeURIComponent(code)}`)).data.organization
+  },
   async me() {
     return (await client.get('/auth/me')).data.user
   },