diff --git a/src/pages/profiler.astro b/src/pages/profiler.astro
index bf8f67c..f620fdd 100644
--- a/src/pages/profiler.astro
+++ b/src/pages/profiler.astro
@@ -164,6 +164,8 @@ const kilde = (p: (typeof profiles)[number]) => {
           setTimeout(function () { btn.textContent = orig; }, 1200);
         }).catch(function () {});
       });
+      var qp = new URLSearchParams(location.search).get('q');
+      if (qp) { search.value = qp; q = qp.trim().toLowerCase(); }
       apply();
     })();
   </script>
diff --git a/src/pages/search-index.json.js b/src/pages/search-index.json.js
index e2b95f5..92f335d 100644
--- a/src/pages/search-index.json.js
+++ b/src/pages/search-index.json.js
@@ -11,6 +11,7 @@ export async function GET() {
     { type: 'page', title: 'Tags', url: '/tags' },
     { type: 'page', title: 'NemHandel-opslag', url: '/nemhandel' },
     { type: 'page', title: 'Profil-opslag (Nemhandel & Peppol)', url: '/profiler' },
+    { type: 'page', title: 'UBL-tjek & identifikator-afkoder', url: '/ubl' },
     { type: 'page', title: 'Spørg mit CV (AI-chat)', url: '/chat' },
     { type: 'page', title: 'Status (homelab)', url: '/status' },
     { type: 'page', title: 'Now', url: '/now' },
diff --git a/src/pages/ubl.astro b/src/pages/ubl.astro
new file mode 100644
index 0000000..5c2a26c
--- /dev/null
+++ b/src/pages/ubl.astro
@@ -0,0 +1,194 @@
+---
+import Base from '../layouts/Base.astro';
+import { profiles } from '../data/profiles';
+
+// Minimal data til klient-matchning (id + customization + navn + standard + dokumenter).
+const idx = profiles.map((p) => ({
+  standard: p.standard,
+  navn: p.navn,
+  id: p.id,
+  customization: p.customization,
+  dokumenter: p.dokumenter,
+}));
+---
+<Base
+  title="UBL-tjek & identifikator-afkoder"
+  description="Træk en UBL/OIOUBL-faktura ind eller indsæt en CustomizationID/ProfileID — så afkoder den profilen, syntaksen og EN 16931-status. Alt sker lokalt i browseren; filen sendes aldrig nogen steder."
+>
+  <h1 class="text-4xl font-bold tracking-tight">UBL-tjek</h1>
+  <p class="mt-4 max-w-2xl text-muted">
+    Træk en <strong class="text-text">UBL/OIOUBL-faktura</strong> (eller andet UBL-dokument) ind — eller indsæt en
+    <strong class="text-text">CustomizationID/ProfileID</strong> — så afkoder den profilen, syntaksen og
+    EN 16931-status og kobler til <a href="/profiler" class="text-accent">profil-opslaget</a>.
+    Alt sker <strong class="text-text">lokalt i din browser</strong>; intet sendes nogen steder.
+  </p>
+
+  <div id="drop" class="mt-8 rounded-2xl border border-dashed border-border bg-surface/40 p-8 text-center transition-colors">
+    <p class="text-muted">Træk en <code class="rounded bg-surface-2 px-1.5 py-0.5">.xml</code>-fil hertil, eller
+      <label class="cursor-pointer text-accent hover:underline">vælg en fil<input id="file" type="file" accept=".xml,text/xml,application/xml" class="hidden" /></label>.
+    </p>
+  </div>
+
+  <details class="mt-3">
+    <summary class="cursor-pointer text-sm text-muted">…eller indsæt XML / en identifikator manuelt</summary>
+    <textarea id="paste" rows="6" placeholder="Indsæt UBL-XML, eller bare en CustomizationID/ProfileID…"
+      class="mt-2 w-full rounded-xl border border-border bg-surface/60 px-4 py-3 font-mono text-xs outline-none focus:border-accent"></textarea>
+    <p class="mt-2"><button id="analyze" type="button" class="rounded-xl bg-accent px-4 py-2 text-sm font-medium text-bg">Afkod</button></p>
+  </details>
+
+  <div id="result" class="mt-6" hidden></div>
+  <p id="err" class="mt-6 text-sm" hidden></p>
+
+  <p class="mt-10 text-xs text-muted/80">
+    Heuristik mod kendte profiler (samme datagrundlag som <a href="/profiler" class="text-accent">/profiler</a>) +
+    EN 16931-/Peppol-/OIOUBL-mønstre. Privat: ingen upload, ingen sporing af indholdet.
+  </p>
+
+  <script type="application/json" id="profiles-data" set:html={JSON.stringify(idx)}></script>
+  <script is:inline>
+    (function () {
+      var PROFILES = JSON.parse(document.getElementById('profiles-data').textContent || '[]');
+      var drop = document.getElementById('drop'), fileInput = document.getElementById('file'),
+          paste = document.getElementById('paste'), result = document.getElementById('result'),
+          err = document.getElementById('err');
+      var esc = function (s) { return String(s == null ? '' : s).replace(/[&<>"]/g, function (c) {
+        return { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;' }[c]; }); };
+
+      // Electronic Address Scheme (ISO 6523) — de gængse, DK/Norden i fokus.
+      var EAS = {
+        '0088': 'GLN (GS1 Global Location Number)',
+        '0184': 'DK:CVR (dansk CVR-nummer)',
+        '0198': 'DK:SE (dansk SE-nummer)',
+        '0096': 'DK:P (dansk P-nummer)',
+        '0192': 'NO:ORG (norsk organisasjonsnummer)',
+        '0007': 'SE:ORG (svensk organisationsnummer)',
+        '0208': 'BE:CBE (belgisk virksomhedsnr.)',
+        '0151': 'AU:ABN', '0060': 'DUNS', '0235': 'JP', '0211': 'IT:PA',
+        '9915': 'Peppol test-deltager', '9930': 'DE:LWID (Leitweg-ID)',
+      };
+
+      function findEl(doc, name) {
+        var all = doc.getElementsByTagName('*');
+        for (var i = 0; i < all.length; i++) if (all[i].localName === name) return all[i];
+        return null;
+      }
+      function txt(doc, name) { var e = findEl(doc, name); return e ? (e.textContent || '').trim() : ''; }
+
+      // afkod en CustomizationID/ProfileID-streng til menneskesprog
+      function decode(custom, profile) {
+        var notes = [], standard = null, match = null;
+        var c = (custom || '').trim(), p = (profile || '').trim();
+
+        // 1) eksakt match mod kendte profiler
+        match = PROFILES.find(function (x) { return c && x.customization === c; })
+             || PROFILES.find(function (x) { return p && x.id === p; })
+             || PROFILES.find(function (x) { return c && x.id === c; });
+
+        // 2) mønster-heuristik (også når der ikke er fuldt match)
+        var blob = (c + ' ' + p).toLowerCase();
+        if (blob.indexOf('en16931') > -1) notes.push('EN 16931-kompatibel (CIUS af den europæiske kernefaktura)');
+        if (blob.indexOf('peppol.eu') > -1 || blob.indexOf('fdc:peppol') > -1) { standard = 'Peppol BIS'; notes.push('Peppol-netværket'); }
+        if (blob.indexOf('pint') > -1) { standard = 'Peppol PINT'; notes.push('PINT (Peppol International)'); }
+        if (blob.indexOf('billing:3.0') > -1) notes.push('Billing 3.0-proces');
+        if (blob.indexOf('selfbilling') > -1) notes.push('Selvfakturering (køber udsteder)');
+        if (blob.indexOf('oioubl') > -1) { standard = standard || 'OIOUBL (NemHandel)'; notes.push('OIOUBL — dansk UBL-tilpasning'); }
+        if (/procurement-/i.test(p)) { standard = standard || 'OIOUBL (NemHandel)'; if (/r-|r$|simr|advr/i.test(p)) notes.push("'R' = svar påkrævet"); }
+
+        return { match: match, standard: match ? match.standard : standard, notes: notes };
+      }
+
+      function badge(text, kind) {
+        var cls = kind === 'ok' ? 'border-accent/40 bg-accent/10 text-accent' : 'border-border bg-surface-2 text-text';
+        return '<span class="rounded-full border ' + cls + ' px-2.5 py-0.5 text-xs">' + esc(text) + '</span>';
+      }
+      function row(dt, dd) {
+        return '<div class="grid gap-1 sm:grid-cols-[10rem_1fr]"><dt class="text-muted">' + esc(dt) +
+          '</dt><dd class="break-all font-mono">' + (dd || '<span class="text-muted">—</span>') + '</dd></div>';
+      }
+
+      function renderXml(doc) {
+        var root = doc.documentElement;
+        var docType = root ? root.localName : '?';
+        var ublv = txt(doc, 'UBLVersionID');
+        var custom = txt(doc, 'CustomizationID');
+        var profile = txt(doc, 'ProfileID');
+        var id = txt(doc, 'ID');
+        var dec = decode(custom, profile);
+
+        // EAS på parter
+        var endpoints = [];
+        var eps = doc.getElementsByTagName('*');
+        for (var i = 0; i < eps.length; i++) {
+          if (eps[i].localName === 'EndpointID') {
+            var scheme = eps[i].getAttribute('schemeID') || '';
+            endpoints.push({ scheme: scheme, val: (eps[i].textContent || '').trim() });
+          }
+        }
+        var epHtml = endpoints.slice(0, 4).map(function (e) {
+          return '<div>' + badge((EAS[e.scheme] || ('EAS ' + e.scheme || 'ukendt')), '') +
+            ' <span class="font-mono text-xs">' + esc(e.val) + '</span></div>';
+        }).join('');
+
+        var head = dec.match
+          ? '<div class="flex flex-wrap items-center gap-2">' + badge(dec.match.standard, 'ok') +
+            '</div><h2 class="mt-2 text-xl font-semibold tracking-tight">' + esc(dec.match.navn) + '</h2>'
+          : '<h2 class="text-xl font-semibold tracking-tight">' + esc(docType) +
+            (dec.standard ? ' <span class="text-muted text-base font-normal">· ' + esc(dec.standard) + '</span>' : '') + '</h2>';
+
+        result.innerHTML =
+          '<div class="rounded-2xl border border-border bg-surface/60 p-5">' + head +
+          '<dl class="mt-3 space-y-1 text-xs">' +
+            row('Dokumenttype', '<span class="font-semibold">' + esc(docType) + '</span> (UBL ' + (esc(ublv) || '2.x') + ')') +
+            row('ID', esc(id)) +
+            row('ProfileID', esc(profile)) +
+            row('CustomizationID', esc(custom)) +
+          '</dl>' +
+          (dec.notes.length ? '<div class="mt-3 flex flex-wrap gap-1.5">' + dec.notes.map(function (n) { return badge(n, ''); }).join('') + '</div>' : '') +
+          (epHtml ? '<p class="mt-3 text-xs text-muted">Parter (EAS):</p><div class="mt-1 space-y-1">' + epHtml + '</div>' : '') +
+          (dec.match ? '<p class="mt-3 text-xs"><a class="text-accent hover:underline" href="/profiler?q=' + encodeURIComponent(dec.match.id) + '">Se profilen i /profiler ↗</a></p>'
+                     : '<p class="mt-3 text-xs text-muted">Ingen eksakt match i profil-databasen — afkodet ud fra mønstre.</p>') +
+          '</div>';
+        result.hidden = false; err.hidden = true;
+      }
+
+      function renderId(s) {
+        var dec = decode(s, s);
+        result.innerHTML = '<div class="rounded-2xl border border-border bg-surface/60 p-5">' +
+          (dec.match ? '<div class="flex flex-wrap items-center gap-2">' + badge(dec.match.standard, 'ok') +
+            '</div><h2 class="mt-2 text-xl font-semibold tracking-tight">' + esc(dec.match.navn) + '</h2>'
+            : '<h2 class="text-xl font-semibold tracking-tight">Identifikator</h2>') +
+          '<dl class="mt-3 space-y-1 text-xs">' + row('Streng', esc(s)) + '</dl>' +
+          (dec.notes.length ? '<div class="mt-3 flex flex-wrap gap-1.5">' + dec.notes.map(function (n) { return badge(n, ''); }).join('') + '</div>'
+            : '<p class="mt-3 text-xs text-muted">Genkendte ingen kendte mønstre.</p>') +
+          (dec.match ? '<p class="mt-3 text-xs"><a class="text-accent hover:underline" href="/profiler?q=' + encodeURIComponent(dec.match.id) + '">Se profilen i /profiler ↗</a></p>' : '') +
+          '</div>';
+        result.hidden = false; err.hidden = true;
+      }
+
+      function analyze(text) {
+        text = (text || '').trim();
+        if (!text) return;
+        if (text.indexOf('<') === 0 || text.indexOf('<?xml') === 0) {
+          var doc = new DOMParser().parseFromString(text, 'application/xml');
+          if (doc.getElementsByTagName('parsererror').length) {
+            err.textContent = 'Kunne ikke parse XML — er filen velformet?'; err.hidden = false; result.hidden = true; return;
+          }
+          renderXml(doc);
+        } else {
+          renderId(text);
+        }
+      }
+
+      // fil-input + drag/drop
+      function readFile(f) { var r = new FileReader(); r.onload = function () { analyze(String(r.result)); }; r.readAsText(f); }
+      fileInput.addEventListener('change', function () { if (fileInput.files[0]) readFile(fileInput.files[0]); });
+      ['dragenter', 'dragover'].forEach(function (ev) { drop.addEventListener(ev, function (e) {
+        e.preventDefault(); drop.classList.add('border-accent'); }); });
+      ['dragleave', 'drop'].forEach(function (ev) { drop.addEventListener(ev, function (e) {
+        e.preventDefault(); drop.classList.remove('border-accent'); }); });
+      drop.addEventListener('drop', function (e) { var f = e.dataTransfer && e.dataTransfer.files[0]; if (f) readFile(f); });
+      document.getElementById('analyze').addEventListener('click', function () { analyze(paste.value); });
+      paste.addEventListener('keydown', function (e) { if ((e.metaKey || e.ctrlKey) && e.key === 'Enter') analyze(paste.value); });
+    })();
+  </script>
+</Base>