diff --git a/src/App.svelte b/src/App.svelte
index 6c93c93..53136b6 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -31,6 +31,7 @@
   import { t } from './lib/i18n/i18n.svelte';
   import { withShortcut } from './lib/i18n/shortcut';
   import { localizeImportMessage } from './lib/i18n/importMessages';
+  import { unavailableFonts } from './lib/utils/fontDetect';
 
   let editor: Editor | null = $state(null);
   let tick: number = $state(0);
@@ -331,6 +332,18 @@
 
   // Replace the document with a parsed .odt; adopt its geometry/header/footer and
   // track the source handle (null for the fallback file input) so Save overwrites it.
+  // Distinct explicit fontFamily values (textStyle marks) anywhere in a TipTap JSON tree.
+  function collectFontFamilies(node: unknown, out: Set<string>): void {
+    if (!node || typeof node !== 'object') return;
+    const n = node as { marks?: { type?: string; attrs?: { fontFamily?: unknown } }[]; content?: unknown[] };
+    if (Array.isArray(n.marks)) {
+      for (const m of n.marks) {
+        if (m?.type === 'textStyle' && typeof m.attrs?.fontFamily === 'string') out.add(m.attrs.fontFamily);
+      }
+    }
+    if (Array.isArray(n.content)) for (const c of n.content) collectFontFamilies(c, out);
+  }
+
   async function applyImport(bytes: Uint8Array, handle: FileSystemFileHandle | null, sourceName?: string) {
     if (!editor) return;
     try {
@@ -369,9 +382,19 @@
       };
       fileHandle = isTemplate ? null : handle;
 
-      if (result.warnings.length) {
-        console.warn('[import] Unsupported content in opened file:', result.warnings);
-        alert(t().dialogs.openedWithLimitations(result.warnings.map(localizeImportMessage).join('\n• ')));
+      // Warn about fonts the document uses but the browser can't render, so text
+      // silently shown in a substitute (Liberation Serif) is at least flagged.
+      const fontSet = new Set<string>();
+      collectFontFamilies(result.content, fontSet);
+      collectFontFamilies(result.header, fontSet);
+      collectFontFamilies(result.footer, fontSet);
+      const missingFonts = await unavailableFonts(fontSet);
+
+      const warnings = result.warnings.map(localizeImportMessage);
+      if (missingFonts.length) warnings.push(t().importWarn.missingFonts(missingFonts.join(', ')));
+      if (warnings.length) {
+        console.warn('[import] Opened file with limitations:', result.warnings, missingFonts);
+        alert(t().dialogs.openedWithLimitations(warnings.join('\n• ')));
       }
     } catch (err) {
       console.error('[import] Failed to open file:', err);
diff --git a/src/lib/i18n/locales/de.ts b/src/lib/i18n/locales/de.ts
index f46e043..2b869ac 100644
--- a/src/lib/i18n/locales/de.ts
+++ b/src/lib/i18n/locales/de.ts
@@ -356,6 +356,7 @@ const de: Messages = {
     nestedTables: 'Verschachtelte Tabellen wurden in Absätze umgewandelt',
     footnotes: 'Fuß- und Endnoten wurden entfernt',
     comments: 'Kommentare wurden entfernt',
+    missingFonts: (fonts) => `Diese Schriftarten sind nicht installiert und wurden durch Ersatzschriften dargestellt: ${fonts}`,
   },
   importError: {
     odtArchive: 'Keine gültige .odt-Datei (Archiv konnte nicht gelesen werden).',
diff --git a/src/lib/i18n/locales/en.ts b/src/lib/i18n/locales/en.ts
index 291529d..0353142 100644
--- a/src/lib/i18n/locales/en.ts
+++ b/src/lib/i18n/locales/en.ts
@@ -361,6 +361,7 @@ const en = {
     nestedTables: 'Nested tables were flattened to paragraphs',
     footnotes: 'Footnotes and endnotes were removed',
     comments: 'Comments were removed',
+    missingFonts: (fonts: string) => `These fonts aren't installed and were shown with a substitute: ${fonts}`,
   },
   importError: {
     odtArchive: 'Not a valid .odt file (could not read the archive).',
diff --git a/src/lib/utils/fontDetect.ts b/src/lib/utils/fontDetect.ts
index f2fab43..d200e59 100644
--- a/src/lib/utils/fontDetect.ts
+++ b/src/lib/utils/fontDetect.ts
@@ -106,6 +106,35 @@ export function detectAvailableFonts(candidates: readonly string[]): string[] {
   return found;
 }
 
+// Families the app always renders via bundled @font-face twins, plus CSS generics —
+// never flagged as missing. The bundled names must match the @font-face in global.css.
+const BUNDLED_FONTS = ['Liberation Serif', 'Times New Roman', 'Calibri', 'Arial', 'Cambria', 'Courier New'];
+const GENERIC_FAMILIES = ['serif', 'sans-serif', 'monospace', 'cursive', 'fantasy', 'system-ui'];
+
+// Of the given family names, those the browser can't render (so text declaring them is
+// silently substituted). Bundled families and generics are excluded; result is deduped.
+export async function unavailableFonts(families: Iterable<string>): Promise<string[]> {
+  const ctx = getCtx();
+  if (!ctx) return [];
+  if (typeof document !== 'undefined' && document.fonts) {
+    try {
+      await Promise.all(BUNDLED_FONTS.map((f) => document.fonts.load(`12px "${f}"`)));
+    } catch { /* measure with whatever loaded */ }
+  }
+  baselineWidths = null;
+  const skip = new Set([...BUNDLED_FONTS, ...GENERIC_FAMILIES].map((f) => f.toLowerCase()));
+  const seen = new Set<string>();
+  const missing: string[] = [];
+  for (const raw of families) {
+    const family = raw.trim();
+    const key = family.toLowerCase();
+    if (!family || seen.has(key) || skip.has(key)) continue;
+    seen.add(key);
+    if (!isAvailable(ctx, family)) missing.push(family);
+  }
+  return missing;
+}
+
 interface LocalFontData { family: string }
 interface QueryLocalFontsWindow {
   queryLocalFonts?: () => Promise<LocalFontData[]>;