diff --git a/README.md b/README.md
index ee0950a..7fa82a7 100644
--- a/README.md
+++ b/README.md
@@ -126,6 +126,22 @@ podman run --replace --name vinterliste \
 The container exposes `/api/health` for healthchecks and bakes the build date /
 git revision into both OCI labels and `/etc/build-info`.
 
+## Registration: open, invite-only, or both
+
+Admins can toggle self-registration from the Admin UI. Two modes:
+
+- **Open** (default): anyone can hit `/` → "Logg inn" → "Opprett konto".
+- **Closed**: the "Opprett konto" button is hidden; new accounts can only
+  be created through invite links.
+
+Any logged-in user can generate invite links from their Profile page. Each
+link is single-use; the link URL is `/<origin>/invite/<token>` and the
+recipient is dropped straight into the signup form with the token attached.
+
+Successful invite-signups record `users.invited_by = <inviter_id>` so the
+account has a traceable origin. Invites that have been claimed are kept in
+the DB (they can no longer be cancelled) so the audit trail survives.
+
 ## Installable (PWA) + mobile
 
 The SPA ships with a web app manifest (`/manifest.webmanifest`), an SVG icon
@@ -156,11 +172,13 @@ There are three privilege levels:
 
 Admin implies moderator — admins automatically pass any `is_moderator` check.
 
-The **first admin** has to be promoted out of band (chicken-and-egg). After
-that, admins can grant moderator/admin to others through the Admin UI.
+The **first user** to sign up is auto-promoted to admin so a fresh
+deployment is never stranded without one. After that, admins can grant
+moderator/admin to others through the Admin UI. If for any reason that
+didn't happen (e.g., you imported a DB), you can still bootstrap manually:
 
 ```bash
-# Bootstrap the first admin:
+# Manually promote (e.g. for imported DBs):
 sqlite3 data/vinterliste.db \
   "UPDATE users SET is_admin = 1 WHERE email = 'you@example.org';"
 
diff --git a/frontend/src/App.svelte b/frontend/src/App.svelte
index 2500b14..efb3a5a 100644
--- a/frontend/src/App.svelte
+++ b/frontend/src/App.svelte
@@ -38,9 +38,11 @@
   let publicListUsername = $state('');
   let activityId = $state('');
   let defaultEmail = $state('');
+  let inviteToken = $state('');
+  let selfRegistryEnabled = $state(true);
 
   interface Route {
-    view: 'public-home' | 'home' | 'public-list' | 'permalink';
+    view: 'public-home' | 'home' | 'public-list' | 'permalink' | 'invite';
     payload?: string;
   }
 
@@ -52,6 +54,8 @@
     if (userList) return { view: 'public-list', payload: userList[1] };
     const perma = path.match(/^\/a\/([A-Za-z0-9-]+)\/?$/);
     if (perma) return { view: 'permalink', payload: perma[1] };
+    const invite = path.match(/^\/invite\/([A-Za-z0-9_-]+)\/?$/);
+    if (invite) return { view: 'invite', payload: invite[1] };
     // Unknown path: treat as the public landing rather than 404. The server
     // returns index.html for anything non-API anyway, so this keeps deep
     // links from looking broken.
@@ -79,6 +83,14 @@
     if (route.view === 'permalink' && route.payload) {
       activityId = route.payload;
     }
+    if (route.view === 'invite' && route.payload) {
+      inviteToken = route.payload;
+    }
+
+    // Pull public site settings so the UI knows whether to show "Opprett konto".
+    api.getSettings()
+      .then((s) => { selfRegistryEnabled = s.self_registry_enabled; })
+      .catch(() => { /* default open if the call fails */ });
 
     // Probe the server for an existing session, but it doesn't change which
     // URL we're rendering — only what content we'd show on /home.
@@ -104,6 +116,12 @@
     } else if (route.view === 'permalink') {
       activityId = route.payload ?? activityId;
       view = 'permalink';
+    } else if (route.view === 'invite') {
+      inviteToken = route.payload ?? inviteToken;
+      // /invite/<token> drops the visitor straight into the signup form with
+      // the token prefilled. If they're already logged in we still show the
+      // landing — they can't claim an invite on top of an existing account.
+      view = session.user ? 'public-home' : 'signup';
     }
   }
 
@@ -176,9 +194,14 @@
       onAuthed={onAuthed}
       onWantSignup={() => (view = 'signup')}
       onWantRecovery={() => (view = 'recovery')}
+      signupAvailable={selfRegistryEnabled}
     />
   {:else if view === 'signup'}
-    <Signup onAuthed={onAuthed} onWantLogin={() => (view = 'login')} />
+    <Signup
+      onAuthed={onAuthed}
+      onWantLogin={() => (view = 'login')}
+      inviteToken={inviteToken}
+    />
   {:else if view === 'recovery'}
     <Recovery onAuthed={onAuthed} onWantLogin={() => (view = 'login')} />
   {:else if view === 'profile'}
diff --git a/frontend/src/components/Admin.svelte b/frontend/src/components/Admin.svelte
index 32ade6e..aff7701 100644
--- a/frontend/src/components/Admin.svelte
+++ b/frontend/src/components/Admin.svelte
@@ -2,7 +2,7 @@
   import { onMount } from 'svelte';
   import { api, ApiError } from '../lib/api';
   import { session } from '../lib/session.svelte';
-  import type { AdminUser } from '../../../shared/types';
+  import type { AdminUser, PublicSettings } from '../../../shared/types';
 
   interface Props {
     onDone: () => void;
@@ -13,7 +13,16 @@
   let loading = $state(true);
   let error: string | null = $state(null);
 
-  onMount(load);
+  let settings: PublicSettings | null = $state(null);
+
+  onMount(async () => {
+    await load();
+    try {
+      settings = await api.getSettings();
+    } catch {
+      // Settings load failure is non-fatal; the toggle just won't render.
+    }
+  });
 
   async function load() {
     loading = true;
@@ -29,6 +38,17 @@
     }
   }
 
+  async function toggleSelfRegistry(next: boolean) {
+    const prev = settings;
+    settings = settings ? { ...settings, self_registry_enabled: next } : settings;
+    try {
+      settings = await api.updateSettings({ self_registry_enabled: next });
+    } catch {
+      settings = prev;
+      error = 'Kunne ikke endre innstilling.';
+    }
+  }
+
   /**
    * Optimistic update: flip the role locally, then send the PATCH. If the
    * server rejects (e.g., last-admin guard fires), reload from the server so
@@ -74,6 +94,24 @@
     om du må.
   </p>
 
+  {#if settings}
+    <div class="card">
+      <h3 style="margin-top: 0;">Selvregistrering</h3>
+      <label class="row" style="gap: 0.5rem; align-items: center;">
+        <input
+          type="checkbox"
+          checked={settings.self_registry_enabled}
+          onchange={(e) => toggleSelfRegistry((e.currentTarget as HTMLInputElement).checked)}
+        />
+        <span>
+          {settings.self_registry_enabled
+            ? 'Åpen — hvem som helst kan opprette konto.'
+            : 'Lukket — bare invitasjonslenker fungerer.'}
+        </span>
+      </label>
+    </div>
+  {/if}
+
   {#if error}<p class="error" role="alert">{error}</p>{/if}
 
   {#if loading}
diff --git a/frontend/src/components/Login.svelte b/frontend/src/components/Login.svelte
index d6d8791..6849a54 100644
--- a/frontend/src/components/Login.svelte
+++ b/frontend/src/components/Login.svelte
@@ -7,8 +7,12 @@
     onAuthed: () => void;
     onWantSignup: () => void;
     onWantRecovery: () => void;
+    /** When false, hide the "Opprett konto" CTA — self-registry is closed
+     *  and the user needs an invite link instead. */
+    signupAvailable?: boolean;
   }
-  let { defaultEmail = '', onAuthed, onWantSignup, onWantRecovery }: Props = $props();
+  let { defaultEmail = '', onAuthed, onWantSignup, onWantRecovery,
+        signupAvailable = true }: Props = $props();
 
   // `defaultEmail` is intentionally used only for the initial value. The warning
   // about referencing a non-state value in `$state(...)` is the right shape of
@@ -65,7 +69,15 @@
     <button class="primary" type="submit" disabled={busy}>
       {busy ? 'Logger inn …' : 'Logg inn'}
     </button>
-    <button type="button" onclick={onWantSignup}>Opprett konto</button>
+    {#if signupAvailable}
+      <button type="button" onclick={onWantSignup}>Opprett konto</button>
+    {/if}
     <button type="button" onclick={onWantRecovery}>Bruk gjenopprettingskode</button>
   </div>
+  {#if !signupAvailable}
+    <p class="muted" style="margin-top: 0.5rem;">
+      Selvregistrering er stengt. Be om en invitasjonslenke fra noen som
+      allerede har konto.
+    </p>
+  {/if}
 </form>
diff --git a/frontend/src/components/Profile.svelte b/frontend/src/components/Profile.svelte
index 04218c9..73aca60 100644
--- a/frontend/src/components/Profile.svelte
+++ b/frontend/src/components/Profile.svelte
@@ -1,7 +1,9 @@
 <script lang="ts">
+  import { onMount } from 'svelte';
   import { api, ApiError } from '../lib/api';
   import { changePassword } from '../lib/auth';
   import { session } from '../lib/session.svelte';
+  import type { InviteEntry } from '../../../shared/types';
 
   interface Props {
     onDone: () => void;
@@ -57,6 +59,62 @@
   let pwSaving = $state(false);
   let pwChanged = $state(false);
 
+  // --- Invites -------------------------------------------------------------
+  let invites: InviteEntry[] = $state([]);
+  let invitesError: string | null = $state(null);
+  let creating = $state(false);
+  let copiedToken: string | null = $state(null);
+
+  async function loadInvites() {
+    try {
+      invites = await api.listInvites();
+    } catch {
+      invitesError = 'Kunne ikke laste invitasjoner.';
+    }
+  }
+
+  onMount(loadInvites);
+
+  async function createInvite() {
+    creating = true;
+    invitesError = null;
+    try {
+      const inv = await api.createInvite();
+      invites = [inv, ...invites];
+    } catch {
+      invitesError = 'Kunne ikke opprette invitasjon.';
+    } finally {
+      creating = false;
+    }
+  }
+
+  async function cancelInvite(inv: InviteEntry) {
+    if (inv.claimed_at) return;
+    if (!confirm('Avbryt denne invitasjonen?')) return;
+    try {
+      await api.cancelInvite(inv.token);
+      invites = invites.filter((i) => i.token !== inv.token);
+    } catch {
+      invitesError = 'Kunne ikke avbryte invitasjonen.';
+    }
+  }
+
+  async function copyInviteUrl(inv: InviteEntry) {
+    try {
+      await navigator.clipboard.writeText(inv.url);
+      copiedToken = inv.token;
+      setTimeout(() => { copiedToken = null; }, 1500);
+    } catch {
+      window.prompt('Kopier denne lenken:', inv.url);
+    }
+  }
+
+  function formatDate(epochMs: number): string {
+    return new Date(epochMs).toLocaleDateString('nb-NO', {
+      year: 'numeric', month: '2-digit', day: '2-digit',
+    });
+  }
+
   async function savePassword(e: SubmitEvent) {
     e.preventDefault();
     pwError = null;
@@ -139,6 +197,49 @@
     </div>
   </form>
 
+  <section class="card" aria-labelledby="inv-h">
+    <h3 id="inv-h">Invitasjonslenker</h3>
+    <p class="muted">
+      Generer en lenke du kan dele. Den som registrerer seg via lenken blir
+      knyttet til deg som invitør. Hver lenke kan bare brukes én gang.
+    </p>
+
+    {#if invitesError}<p class="error" role="alert">{invitesError}</p>{/if}
+
+    <div class="row" style="margin-bottom: 0.5rem;">
+      <button class="primary" type="button" onclick={createInvite} disabled={creating}>
+        {creating ? 'Lager …' : 'Ny invitasjon'}
+      </button>
+    </div>
+
+    {#if invites.length === 0}
+      <p class="muted">Ingen invitasjoner ennå.</p>
+    {/if}
+    {#each invites as inv (inv.token)}
+      <article class="card" style="margin-top: 0.5rem; {inv.claimed_at ? 'opacity: 0.7;' : ''}">
+        <div class="row" style="justify-content: space-between;">
+          <code style="font-size: 0.8rem; word-break: break-all;">{inv.url}</code>
+          <span class="muted" style="white-space: nowrap;">{formatDate(inv.created_at)}</span>
+        </div>
+        <div class="row" style="margin-top: 0.5rem;">
+          {#if inv.claimed_at}
+            <span class="vis-badge semi">Brukt</span>
+            {#if inv.claimed_by_display}
+              <span class="muted">av {inv.claimed_by_display} · {formatDate(inv.claimed_at)}</span>
+            {/if}
+          {:else}
+            <button type="button" onclick={() => copyInviteUrl(inv)}>
+              {copiedToken === inv.token ? 'Kopiert!' : 'Kopier lenke'}
+            </button>
+            <button class="danger" type="button" onclick={() => cancelInvite(inv)}>
+              Avbryt
+            </button>
+          {/if}
+        </div>
+      </article>
+    {/each}
+  </section>
+
   <form onsubmit={savePassword} class="card" aria-labelledby="pw-h">
     <h3 id="pw-h">Bytt passord</h3>
     <p class="muted">
diff --git a/frontend/src/components/Signup.svelte b/frontend/src/components/Signup.svelte
index 46325af..b8273f8 100644
--- a/frontend/src/components/Signup.svelte
+++ b/frontend/src/components/Signup.svelte
@@ -5,8 +5,10 @@
   interface Props {
     onAuthed: () => void;
     onWantLogin: () => void;
+    /** Pre-filled invite token (e.g. from /invite/<token>). Sent on signup. */
+    inviteToken?: string;
   }
-  let { onAuthed, onWantLogin }: Props = $props();
+  let { onAuthed, onWantLogin, inviteToken }: Props = $props();
 
   let email = $state('');
   let password = $state('');
@@ -28,13 +30,29 @@
     }
     busy = true;
     try {
-      const { recoveryCode: code } = await signup(email.trim().toLowerCase(), password);
+      const { recoveryCode: code } = await signup(
+        email.trim().toLowerCase(),
+        password,
+        inviteToken,
+      );
       recoveryCode = code;
       password = '';
       confirm = '';
     } catch (err) {
-      if (err instanceof ApiError && err.status === 409) error = 'Den eposten er allerede i bruk.';
-      else error = 'Kontooppretting feilet.';
+      if (err instanceof ApiError && err.status === 409) {
+        error = 'Den eposten er allerede i bruk.';
+      } else if (err instanceof ApiError && err.status === 403) {
+        const detail = err.detail as { error?: string } | null;
+        if (detail?.error === 'signup_closed') {
+          error = 'Selvregistrering er ikke åpen. Du trenger en invitasjonslenke.';
+        } else if (detail?.error === 'invalid_invite') {
+          error = 'Invitasjonslenken er ugyldig eller allerede brukt.';
+        } else {
+          error = 'Kontooppretting feilet.';
+        }
+      } else {
+        error = 'Kontooppretting feilet.';
+      }
     } finally {
       busy = false;
     }
@@ -55,6 +73,9 @@
 {:else}
   <form onsubmit={submit} class="card" aria-labelledby="signup-h">
     <h2 id="signup-h">Opprett konto</h2>
+    {#if inviteToken}
+      <div class="banner">Du registrerer deg med en invitasjonslenke.</div>
+    {/if}
     <p class="muted">
       Vi krypterer alt du markerer som <em>privat</em> i nettleseren din. Serveren
       ser aldri passordet ditt eller innholdet i private oppføringer.
diff --git a/frontend/src/lib/api.ts b/frontend/src/lib/api.ts
index ff372a6..4094993 100644
--- a/frontend/src/lib/api.ts
+++ b/frontend/src/lib/api.ts
@@ -5,6 +5,7 @@ import type {
   TagSuggestion, ProfileUpdateRequest,
   PublicListResponse, FeedbackSubmitRequest, FeedbackEntry, FeedbackUpdateRequest,
   AdminUser, AdminRoleUpdate,
+  PublicSettings, SettingsUpdateRequest, InviteEntry,
 } from '../../../shared/types';
 
 const BASE = '/api';
@@ -103,4 +104,15 @@ export const api = {
     http<AdminUser>(`/admin/users/${encodeURIComponent(id)}/role`, {
       method: 'PATCH', body: JSON.stringify(body),
     }),
+
+  // --- settings -------------------------------------------------------------
+  getSettings: () => http<PublicSettings>('/settings'),
+  updateSettings: (body: SettingsUpdateRequest) =>
+    http<PublicSettings>('/settings', { method: 'PATCH', body: JSON.stringify(body) }),
+
+  // --- invites --------------------------------------------------------------
+  listInvites: () => http<InviteEntry[]>('/invites'),
+  createInvite: () => http<InviteEntry>('/invites', { method: 'POST' }),
+  cancelInvite: (token: string) =>
+    http<{ ok: true }>(`/invites/${encodeURIComponent(token)}`, { method: 'DELETE' }),
 };
diff --git a/frontend/src/lib/auth.ts b/frontend/src/lib/auth.ts
index e235eb6..f70ba2e 100644
--- a/frontend/src/lib/auth.ts
+++ b/frontend/src/lib/auth.ts
@@ -32,7 +32,11 @@ export interface SignupResult {
  * Signup: generate DEK and both wraps client-side, send wraps + auth verifier
  * to the server.
  */
-export async function signup(email: string, password: string): Promise<SignupResult> {
+export async function signup(
+  email: string,
+  password: string,
+  inviteToken?: string,
+): Promise<SignupResult> {
   await ready();
 
   const dek = generateDek();
@@ -70,6 +74,7 @@ export async function signup(email: string, password: string): Promise<SignupRes
     dek_rec_nonce: bytesToBase64(wrappedRec.nonce),
     rec_auth_salt: bytesToBase64(recAuthSalt),
     rec_auth_verifier: recAuthVerifier,
+    ...(inviteToken ? { invite_token: inviteToken } : {}),
   });
 
   setSession(user, dek);
diff --git a/server/auth.ts b/server/auth.ts
index ed04a4d..82f63aa 100644
--- a/server/auth.ts
+++ b/server/auth.ts
@@ -4,6 +4,8 @@ import {
   currentUserId, issueSession, clearSession, requireAuth, gcSessions,
   type AppVariables,
 } from './session';
+import { isSelfRegistryEnabled } from './settings';
+import { claimInvite } from './invites';
 import type {
   SignupRequest,
   ChallengeResponse,
@@ -124,6 +126,21 @@ authRoutes.post('/signup', async (c) => {
   const existing = db.prepare('SELECT 1 FROM users WHERE email = ?').get(email);
   if (existing) return c.json({ error: 'email_taken' }, 409);
 
+  // Gate: signup requires either (a) self-registry enabled, or (b) a valid
+  // unclaimed invite token. We resolve the invite path even when self-registry
+  // is on so the `invited_by` attribution still records who shared the link.
+  const inviteToken = typeof body.invite_token === 'string' ? body.invite_token.trim() : '';
+  const selfReg = isSelfRegistryEnabled();
+  if (!selfReg && !inviteToken) {
+    return c.json({ error: 'signup_closed' }, 403);
+  }
+
+  // First-user-auto-admin: count rows *before* the insert. If this is the
+  // first user, they become admin so the deployment is never stranded
+  // without one. (Documented in README.)
+  const userCount = (db.prepare('SELECT COUNT(*) AS n FROM users').get() as { n: number }).n;
+  const isFirstUser = userCount === 0;
+
   // Server-side hash of the client-derived verifier. The verifier is already
   // expensive to brute-force (Argon2id-MODERATE), so Bun.password adds a second
   // hardening layer in case the DB leaks but the verifier salt is still public.
@@ -136,27 +153,52 @@ authRoutes.post('/signup', async (c) => {
 
   const id = newId();
   const now = Date.now();
-  db.prepare(`
-    INSERT INTO users
-      (id, email, auth_salt, auth_verifier_hash, kek_salt,
-       wrapped_dek_pw, dek_pw_nonce, wrapped_dek_rec, rec_salt, dek_rec_nonce,
-       rec_auth_salt, rec_auth_verifier_hash, created_at)
-    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-  `).run(
-    id,
-    email,
-    b64ToBuffer(body.auth_salt),
-    verifierHash,
-    b64ToBuffer(body.kek_salt),
-    b64ToBuffer(body.wrapped_dek_pw),
-    b64ToBuffer(body.dek_pw_nonce),
-    b64ToBuffer(body.wrapped_dek_rec),
-    b64ToBuffer(body.rec_salt),
-    b64ToBuffer(body.dek_rec_nonce),
-    b64ToBuffer(body.rec_auth_salt),
-    recVerifierHash,
-    now,
-  );
+
+  // The user-insert and the invite-claim must commit or fail together: a
+  // claimed invite pointing at a nonexistent user (or a user without their
+  // claimed invite recorded) would be an audit-trail inconsistency.
+  let invitedBy: string | null = null;
+  try {
+    db.transaction(() => {
+      if (inviteToken) {
+        const inviter = claimInvite(inviteToken, id);
+        if (!inviter) {
+          if (!selfReg) throw new Error('invalid_invite');
+          // self-registry on + bad token = proceed without attribution
+        } else {
+          invitedBy = inviter;
+        }
+      }
+      db.prepare(`
+        INSERT INTO users
+          (id, email, auth_salt, auth_verifier_hash, kek_salt,
+           wrapped_dek_pw, dek_pw_nonce, wrapped_dek_rec, rec_salt, dek_rec_nonce,
+           rec_auth_salt, rec_auth_verifier_hash, is_admin, invited_by, created_at)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+      `).run(
+        id,
+        email,
+        b64ToBuffer(body.auth_salt),
+        verifierHash,
+        b64ToBuffer(body.kek_salt),
+        b64ToBuffer(body.wrapped_dek_pw),
+        b64ToBuffer(body.dek_pw_nonce),
+        b64ToBuffer(body.wrapped_dek_rec),
+        b64ToBuffer(body.rec_salt),
+        b64ToBuffer(body.dek_rec_nonce),
+        b64ToBuffer(body.rec_auth_salt),
+        recVerifierHash,
+        isFirstUser ? 1 : 0,
+        invitedBy,
+        now,
+      );
+    })();
+  } catch (err) {
+    if (err instanceof Error && err.message === 'invalid_invite') {
+      return c.json({ error: 'invalid_invite' }, 403);
+    }
+    throw err;
+  }
 
   issueSession(c, id);
   gcSessions();
diff --git a/server/db.ts b/server/db.ts
index 5d20744..776a072 100644
--- a/server/db.ts
+++ b/server/db.ts
@@ -35,9 +35,12 @@ const SCHEMA_STATEMENTS: readonly string[] = [
     is_moderator INTEGER NOT NULL DEFAULT 0,
     -- Admin flag. Strictly stronger than moderator: admins have everything
     -- moderators have, plus the /api/admin/* endpoints (promote/demote other
-    -- users). Bootstrapped via "sqlite3 ... UPDATE" (see README); after that,
-    -- admins can grant moderator/admin to others through the UI.
+    -- users). The first user to sign up is auto-promoted to admin so the
+    -- deployment is never stranded without one; after that, admins can
+    -- grant moderator/admin to others through the UI.
     is_admin INTEGER NOT NULL DEFAULT 0,
+    -- Inviter, if this account was created via an invite token. Nullable.
+    invited_by TEXT REFERENCES users(id),
     -- Optional public URL slug. When set + opt-in, the user's public
     -- activities are reachable at "/<username>/list". Distinct from
     -- display_name because URL slugs need uniqueness and shape constraints
@@ -105,6 +108,24 @@ const SCHEMA_STATEMENTS: readonly string[] = [
     PRIMARY KEY (activity_id, user_id)
   )`,
   `CREATE INDEX IF NOT EXISTS activity_hearts_user_idx ON activity_hearts(user_id)`,
+  // Global settings (key/value). Currently used for self_registry_enabled
+  // but kept generic so future toggles don't need their own table.
+  `CREATE TABLE IF NOT EXISTS settings (
+    key TEXT PRIMARY KEY,
+    value TEXT NOT NULL,
+    updated_at INTEGER NOT NULL
+  )`,
+  // Invites: any logged-in user generates a token; signup-via-token records
+  // the inviter so accounts have a traceable origin. Tokens are
+  // single-use; claimed_* are set when a signup consumes one.
+  `CREATE TABLE IF NOT EXISTS invites (
+    token TEXT PRIMARY KEY,
+    inviter_user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    created_at INTEGER NOT NULL,
+    claimed_at INTEGER,
+    claimed_by_user_id TEXT REFERENCES users(id)
+  )`,
+  `CREATE INDEX IF NOT EXISTS invites_inviter_idx ON invites(inviter_user_id)`,
 ];
 
 const PRAGMAS: readonly string[] = [
@@ -159,6 +180,7 @@ export function getDb(): Database {
   ensureColumn(db, 'users', 'display_name', 'TEXT');
   ensureColumn(db, 'users', 'is_moderator', 'INTEGER NOT NULL DEFAULT 0');
   ensureColumn(db, 'users', 'is_admin', 'INTEGER NOT NULL DEFAULT 0');
+  ensureColumn(db, 'users', 'invited_by', 'TEXT');
   // Feedback triage columns (added after the feedback feature shipped).
   ensureColumn(db, 'feedback', 'done_at', 'INTEGER');
   ensureColumn(db, 'feedback', 'done_by', 'TEXT');
diff --git a/server/index.ts b/server/index.ts
index 4584d04..ccf3cc4 100644
--- a/server/index.ts
+++ b/server/index.ts
@@ -7,6 +7,8 @@ import { tagsRoutes } from './tags';
 import { usersRoutes } from './users';
 import { feedbackRoutes } from './feedback';
 import { adminRoutes } from './admin';
+import { settingsRoutes } from './settings';
+import { invitesRoutes } from './invites';
 
 // Initialise DB up front so the server fails fast on schema problems.
 getDb();
@@ -29,6 +31,8 @@ app.route('/api/tags', tagsRoutes);
 app.route('/api/users', usersRoutes);
 app.route('/api/feedback', feedbackRoutes);
 app.route('/api/admin', adminRoutes);
+app.route('/api/settings', settingsRoutes);
+app.route('/api/invites', invitesRoutes);
 
 // In production, serve the built Svelte SPA. The static helper is registered
 // for the asset directory and for the top-level files that Vite copies from
diff --git a/server/invites.ts b/server/invites.ts
new file mode 100644
index 0000000..80e4fc9
--- /dev/null
+++ b/server/invites.ts
@@ -0,0 +1,136 @@
+import { Hono } from 'hono';
+import { getDb } from './db';
+import { requireAuth, type AppVariables } from './session';
+import type { InviteEntry } from '../shared/types';
+
+/**
+ * Invite tokens. Any logged-in user can create one and share it; signup-via-
+ * token records the inviter on the new user and marks the invite claimed.
+ *
+ * Tokens are single-use: each invite either has no `claimed_at` (still usable)
+ * or one (consumed, forever). To "regenerate" you delete-and-create.
+ *
+ * Token format: 22-char base64url of 16 random bytes (~128 bits of entropy).
+ * Long enough to be unguessable, short enough to share verbatim in chat.
+ */
+export const invitesRoutes = new Hono<{ Variables: AppVariables }>();
+
+function newToken(): string {
+  const buf = new Uint8Array(16);
+  crypto.getRandomValues(buf);
+  return Buffer.from(buf)
+    .toString('base64')
+    .replaceAll('+', '-')
+    .replaceAll('/', '_')
+    .replace(/=+$/, '');
+}
+
+interface InviteRow {
+  token: string;
+  inviter_user_id: string;
+  created_at: number;
+  claimed_at: number | null;
+  claimed_by_user_id: string | null;
+  claimed_display_name: string | null;
+  claimed_email: string | null;
+}
+
+function toEntry(row: InviteRow, origin: string): InviteEntry {
+  let claimedByDisplay: string | null = null;
+  if (row.claimed_at && row.claimed_email) {
+    if (row.claimed_display_name && row.claimed_display_name.trim()) {
+      claimedByDisplay = row.claimed_display_name;
+    } else {
+      const at = row.claimed_email.indexOf('@');
+      claimedByDisplay = at > 0 ? row.claimed_email.slice(0, at) : row.claimed_email;
+    }
+  }
+  return {
+    token: row.token,
+    url: `${origin}/invite/${row.token}`,
+    created_at: row.created_at,
+    claimed_at: row.claimed_at,
+    claimed_by_display: claimedByDisplay,
+  };
+}
+
+/**
+ * Validate a token and atomically mark it claimed. Returns the inviter id
+ * if the token was valid + unclaimed; null otherwise. Called from signup.
+ */
+export function claimInvite(token: string, claimerUserId: string): string | null {
+  const db = getDb();
+  const row = db
+    .prepare('SELECT inviter_user_id, claimed_at FROM invites WHERE token = ?')
+    .get(token) as { inviter_user_id: string; claimed_at: number | null } | null;
+  if (!row) return null;
+  if (row.claimed_at !== null) return null;
+
+  // Two near-simultaneous claims could both pass the check above. Make the
+  // claim conditional on claimed_at still being NULL so only one wins.
+  const res = db
+    .prepare('UPDATE invites SET claimed_at = ?, claimed_by_user_id = ? WHERE token = ? AND claimed_at IS NULL')
+    .run(Date.now(), claimerUserId, token);
+  if (res.changes === 0) return null;
+  return row.inviter_user_id;
+}
+
+function originOf(c: { req: { url: string } }): string {
+  const u = new URL(c.req.url);
+  return `${u.protocol}//${u.host}`;
+}
+
+// --- GET /api/invites -------------------------------------------------------
+// List the caller's invites (active first, then claimed).
+invitesRoutes.get('/', requireAuth, (c) => {
+  const userId = c.get('userId');
+  const rows = getDb()
+    .prepare(`
+      SELECT i.token, i.inviter_user_id, i.created_at, i.claimed_at,
+             i.claimed_by_user_id,
+             u.display_name AS claimed_display_name,
+             u.email AS claimed_email
+      FROM invites i
+      LEFT JOIN users u ON u.id = i.claimed_by_user_id
+      WHERE i.inviter_user_id = ?
+      ORDER BY (i.claimed_at IS NOT NULL) ASC, i.created_at DESC
+    `)
+    .all(userId) as InviteRow[];
+  return c.json(rows.map((r) => toEntry(r, originOf(c))));
+});
+
+// --- POST /api/invites ------------------------------------------------------
+invitesRoutes.post('/', requireAuth, (c) => {
+  const userId = c.get('userId');
+  const token = newToken();
+  getDb()
+    .prepare('INSERT INTO invites (token, inviter_user_id, created_at) VALUES (?, ?, ?)')
+    .run(token, userId, Date.now());
+
+  const row = getDb()
+    .prepare(`
+      SELECT i.token, i.inviter_user_id, i.created_at, i.claimed_at,
+             i.claimed_by_user_id,
+             NULL AS claimed_display_name, NULL AS claimed_email
+      FROM invites i WHERE i.token = ?
+    `)
+    .get(token) as InviteRow;
+  return c.json(toEntry(row, originOf(c)), 201);
+});
+
+// --- DELETE /api/invites/:token ---------------------------------------------
+// Cancel an unused invite. Refuses to delete already-claimed invites so the
+// audit trail (who-invited-whom) survives.
+invitesRoutes.delete('/:token', requireAuth, (c) => {
+  const userId = c.get('userId');
+  const token = c.req.param('token');
+  const db = getDb();
+  const row = db
+    .prepare('SELECT inviter_user_id, claimed_at FROM invites WHERE token = ?')
+    .get(token) as { inviter_user_id: string; claimed_at: number | null } | null;
+  if (!row) return c.json({ error: 'not_found' }, 404);
+  if (row.inviter_user_id !== userId) return c.json({ error: 'forbidden' }, 403);
+  if (row.claimed_at !== null) return c.json({ error: 'already_claimed' }, 409);
+  db.prepare('DELETE FROM invites WHERE token = ?').run(token);
+  return c.json({ ok: true });
+});
diff --git a/server/settings.ts b/server/settings.ts
new file mode 100644
index 0000000..5ea82f3
--- /dev/null
+++ b/server/settings.ts
@@ -0,0 +1,69 @@
+import { Hono } from 'hono';
+import { getDb } from './db';
+import { requireAuth, type AppVariables } from './session';
+import { isAdmin } from './roles';
+import type { PublicSettings, SettingsUpdateRequest } from '../shared/types';
+
+/**
+ * Global site settings. Generic key/value table so future toggles don't each
+ * need their own column. Keys are validated against a whitelist (`KNOWN`)
+ * before write so we don't accumulate junk rows from typos or curious admins.
+ */
+export const settingsRoutes = new Hono<{ Variables: AppVariables }>();
+
+const KNOWN = new Set<string>(['self_registry_enabled']);
+const DEFAULTS: Record<string, string> = {
+  // Default to allowing signup so a fresh deployment is usable. An admin
+  // can disable it once they've bootstrapped their account.
+  self_registry_enabled: '1',
+};
+
+function readRaw(key: string): string {
+  const row = getDb()
+    .prepare('SELECT value FROM settings WHERE key = ?')
+    .get(key) as { value: string } | null;
+  return row?.value ?? DEFAULTS[key] ?? '';
+}
+
+function writeRaw(key: string, value: string): void {
+  getDb()
+    .prepare(`
+      INSERT INTO settings (key, value, updated_at) VALUES (?, ?, ?)
+      ON CONFLICT(key) DO UPDATE SET value = excluded.value, updated_at = excluded.updated_at
+    `)
+    .run(key, value, Date.now());
+}
+
+/** Boolean helper used by signup. */
+export function isSelfRegistryEnabled(): boolean {
+  return readRaw('self_registry_enabled') === '1';
+}
+
+function publicSnapshot(): PublicSettings {
+  return {
+    self_registry_enabled: readRaw('self_registry_enabled') === '1',
+  };
+}
+
+// --- GET /api/settings ------------------------------------------------------
+// Public: clients need to know whether to show the "Opprett konto" button on
+// the login screen. Nothing sensitive here.
+settingsRoutes.get('/', (c) => c.json(publicSnapshot()));
+
+// --- PATCH /api/settings ----------------------------------------------------
+// Admin-only.
+settingsRoutes.patch('/', requireAuth, async (c) => {
+  const userId = c.get('userId');
+  if (!isAdmin(userId)) return c.json({ error: 'forbidden' }, 403);
+
+  const body = (await c.req.json().catch(() => null)) as SettingsUpdateRequest | null;
+  if (!body) return c.json({ error: 'invalid_json' }, 400);
+
+  for (const [k, v] of Object.entries(body)) {
+    if (!KNOWN.has(k)) return c.json({ error: `unknown_key:${k}` }, 400);
+    if (typeof v !== 'boolean') return c.json({ error: `invalid:${k}` }, 400);
+    writeRaw(k, v ? '1' : '0');
+  }
+
+  return c.json(publicSnapshot());
+});
diff --git a/shared/types.ts b/shared/types.ts
index 1262435..d1ff2be 100644
--- a/shared/types.ts
+++ b/shared/types.ts
@@ -22,6 +22,33 @@ export interface SignupRequest {
   // verifier, recovery-complete is rejected (closing the lockout DoS).
   rec_auth_salt: string;
   rec_auth_verifier: string;
+  /**
+   * Optional invite token. Required when self-registry is disabled.
+   * When present and valid, the new user's `invited_by` is set to the
+   * inviter and the invite is marked claimed.
+   */
+  invite_token?: string;
+}
+
+// --- Site settings ---------------------------------------------------------
+/** Subset of settings exposed to anonymous clients (gates the signup UI). */
+export interface PublicSettings {
+  self_registry_enabled: boolean;
+}
+
+export interface SettingsUpdateRequest {
+  self_registry_enabled?: boolean;
+}
+
+// --- Invites ---------------------------------------------------------------
+export interface InviteEntry {
+  token: string;
+  /** Absolute URL the inviter shares: <origin>/invite/<token>. */
+  url: string;
+  created_at: number;
+  claimed_at: number | null;
+  /** Display name (or email prefix) of the user who claimed it, if any. */
+  claimed_by_display: string | null;
 }
 
 export interface ChallengeResponse {