Locale-aware defaults: browser language list + US Letter/A4 paper size

Language inference:
- Walk navigator.languages (the full ordered preference list), not just
  navigator.language, and pick the first base language we support. A user who
  prefers e.g. Dutch then German now gets German instead of the English
  fallback. De-duplicates the default-language resolution into setDefaultText.

Paper size (US Letter + A4):
- Add A4 (210x297mm) alongside US Letter (8.5x11in). Sheet dimensions move to
  CSS custom properties (--sheet-w/--sheet-h) toggled by a paper-letter/paper-a4
  class on <html>; the tear-off column and QR codes stay fixed physical sizes
  and the content column flexes.
- @page size is injected by JS (id voxvera-page-size) since @page cannot read
  CSS variables across engines; the print block keeps margin:0 and a Letter
  default for the pre-JS state.
- Default paper is chosen from the browser locale's region subtag
  (en-US -> Letter, en-GB/de-DE -> A4) — "by location" without geolocation,
  falling back to Letter when no region is present. A manual override selector
  (topbar + viewer controls) persists in localStorage and wins over the default.
- Paper size is a local print/view preference and is never written into the
  Nostr event, so a flyer reprints on either size unchanged.
- Add paper_size/paper_letter/paper_a4 labels for all 14 languages.

Docs + tests:
- Spec gains a "Print paper size" section; AGENTS.md records the
  not-in-payload invariant; README adds a feature bullet; the field-limits
  cheat sheet gains Letter/A4 columns (re-measured per paper size).
- Playwright: add tests for navigator.languages inference, region-based paper
  default (A4 and Letter), and override persistence. 54 tests pass across
  Chromium, Firefox, WebKit, and Android/iOS mobile emulations.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

AGENTS.md

@@ -19,6 +19,7 @@
 - Treat Nostr event content as untrusted. Escape rendered content and reject unsafe schema input.
 - Preserve print behavior: app controls must not print or shift the flyer sheet in print output.
 - Preserve the old flyer visual language unless the user explicitly asks for a redesign.
+- Paper size (US Letter / A4) is a local print/view preference (`localStorage`), defaulted from the browser locale region. Never write it into the Nostr event — a flyer must reprint on either size without changing the source event.
 
 ## Localization
 

README.md

@@ -15,7 +15,8 @@ The previous Tor/OnionShare CLI version is preserved on the `legacy-tor` branch.
 - **Tear-off tabs.** The printable flyer has ten tear-off tabs. Each tab is a single hyperlinked call to action (the URL is the link, not printed as text) and prints the full event ID so anyone can re-find the flyer by typing it.
 - **Loading state on shared links.** Opening a poster/event link shows a localized "Loading content…" placeholder (and a "Could not load this flyer." state on failure) instead of the default flyer; the default sample content appears only on the bare site URL.
 - **14 languages with RTL support.** Flyer content and UI are localized; right-to-left scripts render correctly. Letter-spacing is applied per script so cursive (Arabic/Persian) and combining (Devanagari) scripts are not broken — see [the spec](docs/nostr-static-client-spec.md#letter-spacing-by-script).
-- **Fits-the-page editing.** Fields that would overflow the printable sheet are rejected as you type, with an inline error under the affected field. See the [field length cheat sheet](docs/flyer-field-limits.md) for how much text fits each field per language.
+- **US Letter and A4.** Print size defaults to the right paper for the visitor's country (from the browser locale's region — `en-US` → Letter, `en-GB` → A4, no geolocation), with a manual override. Paper size is a local print preference and is never written into the event. See the [spec](docs/nostr-static-client-spec.md#print-paper-size).
+- **Fits-the-page editing.** Fields that would overflow the printable sheet are rejected as you type, with an inline error under the affected field. See the [field length cheat sheet](docs/flyer-field-limits.md) for how much text fits each field per language and paper size.
 - **QR codes.** The tear-off QR points at the poster URL (re-open and reprint); the main flyer QR points at the creator's content URL.
 - **Self-contained.** No build step and no CDNs — Nostr and QR libraries are vendored under `site/vendor/`.
 

docs/flyer-field-limits.md

@@ -9,7 +9,8 @@ So the real limit is enforced for you as you type — the numbers below are
 practical guidance for drafting copy, sizing translations, or prompting an LLM
 to write flyer text that will fit on the first try.
 
-Capacity varies by **script**, not by individual language, for three reasons:
+Capacity varies by **script** (not by individual language) and by **paper
+size**, for these reasons:
 
 1. The flyer body font is monospace (`Courier New`), so within a script every
    character takes the same width regardless of upper/lowercase.
@@ -17,19 +18,22 @@ Capacity varies by **script**, not by individual language, for three reasons:
    [`nostr-static-client-spec.md`](nostr-static-client-spec.md#letter-spacing-by-script)).
 3. Glyph width differs by script — CJK glyphs are full-width (≈2× a Latin
    character), Devanagari fallback glyphs are narrower, etc.
+4. **Paper size.** A4 (210×297mm) is slightly narrower and taller than US
+   Letter (8.5×11in), so single-line fields hold ~2 fewer characters on A4
+   while the body holds a little more. Both sizes are shown below.
 
 ## Single-line fields (hard caps)
 
 **Title**, **Subtitle**, and **Headline** are single-line: they never wrap, so
 these are the limits people actually run into. Counts are characters
-(codepoints).
+(codepoints), shown as **Letter / A4**.
 
-| Languages | Title | Headline | Subtitle |
-|---|---|---|---|
-| Latin & Cyrillic & Hebrew — en, es, de, fr, pt, sw, tr, ru, he | ~28 | ~28 | ~32 |
-| Arabic & Persian — ar, fa | ~28 | ~28 | ~38 |
-| Devanagari — hi | ~36 | ~36 | ~51 |
-| CJK — ja, zh | ~17 | ~17 | ~23 |
+| Languages | Title & Headline | Subtitle |
+|---|---|---|
+| Latin & Cyrillic & Hebrew — en, es, de, fr, pt, sw, tr, ru, he | ~28 / ~26 | ~32 / ~30 |
+| Arabic & Persian — ar, fa | ~28 / ~27 | ~38 / ~36 |
+| Devanagari — hi | ~36 / ~35 | ~51 / ~48 |
+| CJK — ja, zh | ~17 / ~16 | ~23 / ~21 |
 
 ## Multi-line fields (generous)
 
@@ -37,12 +41,12 @@ these are the limits people actually run into. Counts are characters
 (`footer_message`) wrap across multiple lines, so they hold far more and are
 bounded only by the remaining height of the sheet.
 
-| Languages | Body (content) |
+| Languages | Body (content) — Letter / A4 |
 |---|---|
-| Latin & Cyrillic & Hebrew | ~1,900 (a few hundred words) |
-| Arabic & Persian | ~1,850 |
-| Devanagari — hi | ~2,450 |
-| CJK — ja, zh | ~1,170 |
+| Latin & Cyrillic & Hebrew | ~1,900 / ~2,000 (a few hundred words) |
+| Arabic & Persian | ~1,850 / ~1,930 |
+| Devanagari — hi | ~2,450 / ~2,545 |
+| CJK — ja, zh | ~1,170 / ~1,220 |
 
 `url_message` and `footer_message` share the lower portion of the sheet and can
 hold roughly 1,200–4,800 characters depending on script, but for a readable
@@ -55,7 +59,7 @@ URLs scan more reliably).
 ## Notes and caveats
 
 - **Approximate.** These come from rendering each script in a headless browser
-  at true print size (8.5in × 11in, content column 4.75in). The
+  at true print size for both Letter (8.5×11in) and A4 (210×297mm). The
   Latin/Cyrillic numbers (`Courier New`) are the most reliable; numbers for
   Hebrew, Arabic, Persian, Devanagari, and CJK depend on the system fallback
   font, which can differ slightly between devices and from print output.

docs/nostr-static-client-spec.md

@@ -122,6 +122,36 @@ The client and schema helper must:
 - keep attachments unsupported in V1
 - avoid remote frontend dependencies
 
+## Print paper size
+
+The flyer supports two print sizes: **US Letter** (8.5×11in) and **A4**
+(210×297mm), covering every country whose language the client supports (Letter
+in North America and a few Latin American countries; A4 everywhere else,
+including the EU, Russia, China, Japan, and the Middle East).
+
+- Dimensions live in CSS custom properties `--sheet-w` / `--sheet-h`, switched
+  by a `paper-letter` / `paper-a4` class on `<html>` (`applyPaperSize` in
+  `nostr-client.js`). The tear-off column (`3.75in`) and QR codes (`1.25in`)
+  stay fixed physical sizes; the content column flexes to the sheet width.
+- The print `@page { size: … }` is injected by JS (an element with id
+  `voxvera-page-size`), because `@page size` cannot read CSS custom properties
+  across engines. The static `@media print` block keeps `margin: 0` and a
+  Letter default for the pre-JS state.
+- The default is chosen from the **region subtag** of the browser locale
+  (`preferredPaperSize` — e.g. `en-GB` → A4, `en-US` → Letter). This is "by
+  location" without geolocation, using the same signal as language. When no
+  locale carries a region, it falls back to Letter.
+- A user override (the paper-size selector) is stored in `localStorage`
+  (`voxvera_paper`) and wins over the region default.
+- **Paper size is a local print/view preference and is never written into the
+  Nostr event.** A flyer authored on Letter reprints on A4 for a European
+  viewer without changing the source event. The live fit-check protects
+  authoring on whichever size is active; switching to a narrower size after
+  authoring can ellipsis-truncate a maxed-out single-line field.
+
+Field capacity therefore varies by paper size; see
+[`flyer-field-limits.md`](flyer-field-limits.md).
+
 ## Localization
 
 Flyer defaults come from `site/locales.js`.

e2e/flyer.spec.js

@@ -86,4 +86,64 @@ test.describe("VoxVera static client", () => {
     );
     await expect(page.locator(".content h1")).toHaveCount(0);
   });
+
+  test("infers language from the first supported browser preference", async ({ page }) => {
+    // Browser prefers Dutch (unsupported), then German (supported), then
+    // English. We should honor German rather than jumping to the English
+    // fallback — i.e. walk navigator.languages, not just navigator.language.
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, "languages", {
+        configurable: true,
+        get: () => ["nl-NL", "de-DE", "en-US"]
+      });
+      Object.defineProperty(navigator, "language", {
+        configurable: true,
+        get: () => "nl-NL"
+      });
+    });
+    await page.goto("/");
+    // German default headline (locales.js de.landing.title).
+    await expect(page.locator(".content h1").first()).toContainText("STRENG GEHEIM");
+    await expect(page.locator("html")).toHaveAttribute("lang", "de");
+  });
+
+  test("defaults to A4 for an A4-region locale (no geolocation)", async ({ page }) => {
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, "languages", { configurable: true, get: () => ["de-DE"] });
+      Object.defineProperty(navigator, "language", { configurable: true, get: () => "de-DE" });
+    });
+    await page.goto("/");
+    await expect(page.locator("html")).toHaveClass(/paper-a4/);
+    const pageRule = await page.evaluate(
+      () => document.getElementById("voxvera-page-size").textContent
+    );
+    expect(pageRule).toContain("A4");
+  });
+
+  test("defaults to US Letter for a Letter-region locale", async ({ page }) => {
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, "languages", { configurable: true, get: () => ["en-US"] });
+      Object.defineProperty(navigator, "language", { configurable: true, get: () => "en-US" });
+    });
+    await page.goto("/");
+    await expect(page.locator("html")).toHaveClass(/paper-letter/);
+    const pageRule = await page.evaluate(
+      () => document.getElementById("voxvera-page-size").textContent
+    );
+    expect(pageRule).toContain("Letter");
+  });
+
+  test("manual paper-size override persists across reloads", async ({ page }) => {
+    await page.addInitScript(() => {
+      Object.defineProperty(navigator, "languages", { configurable: true, get: () => ["en-US"] });
+    });
+    // Editor mode shows the topbar controls; viewer mode hides them.
+    await page.goto("/#editor");
+    await expect(page.locator("html")).toHaveClass(/paper-letter/);
+    await page.locator("#topbar-paper").selectOption("a4");
+    await expect(page.locator("html")).toHaveClass(/paper-a4/);
+    await page.reload();
+    // Stored override beats the en-US region default.
+    await expect(page.locator("html")).toHaveClass(/paper-a4/);
+  });
 });

site/index.html

@@ -18,6 +18,7 @@
         <button id="viewer-tab" class="tab" type="button" data-mode="viewer">Viewer</button>
       </nav>
       <select id="topbar-lang" aria-label="Language"></select>
+      <select id="topbar-paper" aria-label="Paper size"></select>
     </div>
   </header>
 
@@ -26,6 +27,7 @@
     <button type="button" id="viewer-print">Print</button>
     <button type="button" id="viewer-editor">Editor</button>
     <select id="viewer-lang" aria-label="Language"></select>
+    <select id="viewer-paper" aria-label="Paper size"></select>
   </div>
 
   <main>

site/nostr-client.css

@@ -7,6 +7,21 @@
   --accent: #b80000;
   --ok: #1d6b3a;
   --warn: #8a4d00;
+  /* Printable sheet dimensions. Switched by the paper-* class on <html>
+     (applyPaperSize in nostr-client.js). The tear-off column (3.75in) and QR
+     codes (1.25in) stay fixed physical sizes; the content column flexes. */
+  --sheet-w: 8.5in;
+  --sheet-h: 11in;
+}
+
+html.paper-letter {
+  --sheet-w: 8.5in;
+  --sheet-h: 11in;
+}
+
+html.paper-a4 {
+  --sheet-w: 210mm;
+  --sheet-h: 297mm;
 }
 
 * {
@@ -278,8 +293,8 @@ code {
 
 .flyer-sheet {
   display: flex;
-  width: 8.5in;
-  height: 11in;
+  width: var(--sheet-w);
+  height: var(--sheet-h);
   border: 1px solid #000;
   background: #fff;
   color: #000;
@@ -374,8 +389,8 @@ a {
 .container {
   display: flex;
   flex-direction: row;
-  width: 8.5in;
-  height: 11in;
+  width: var(--sheet-w);
+  height: var(--sheet-h);
   border: 1px solid #000;
   background: #fff;
   color: #000;
@@ -502,7 +517,7 @@ a {
 }
 
 .content {
-  width: calc(8.5in - 3.75in);
+  width: calc(var(--sheet-w) - 3.75in);
   padding: 15px 20px;
   text-align: center;
   box-sizing: border-box;
@@ -880,6 +895,9 @@ body.mode-viewer #viewer-panel.drawer-open .result-panel {
 }
 
 @media print {
+  /* @page size is injected by applyPaperSize() in nostr-client.js (Letter or
+     A4) since @page cannot read CSS custom properties across engines. This
+     rule is the margin fallback and the default size before JS runs. */
   @page {
     size: Letter portrait;
     margin: 0;
@@ -887,8 +905,8 @@ body.mode-viewer #viewer-panel.drawer-open .result-panel {
 
   html,
   body {
-    width: 8.5in;
-    height: 11in;
+    width: var(--sheet-w);
+    height: var(--sheet-h);
     margin: 0;
     padding: 0;
     overflow: hidden;
@@ -910,16 +928,16 @@ body.mode-viewer #viewer-panel.drawer-open .result-panel {
 
   main {
     display: block;
-    width: 8.5in;
-    height: 11in;
+    width: var(--sheet-w);
+    height: var(--sheet-h);
     padding: 0;
     margin: 0;
   }
 
   .preview-band {
     display: block;
-    width: 8.5in;
-    height: 11in;
+    width: var(--sheet-w);
+    height: var(--sheet-h);
     border: 0;
     margin: 0;
     padding: 0;
@@ -927,8 +945,8 @@ body.mode-viewer #viewer-panel.drawer-open .result-panel {
 
   .flyer-preview {
     display: block;
-    width: 8.5in;
-    height: 11in;
+    width: var(--sheet-w);
+    height: var(--sheet-h);
     overflow: visible;
     padding: 0;
     margin: 0;
@@ -938,8 +956,8 @@ body.mode-viewer #viewer-panel.drawer-open .result-panel {
   .container {
     position: absolute;
     inset: 0 auto auto 0;
-    width: 8.5in;
-    height: 11in;
+    width: var(--sheet-w);
+    height: var(--sheet-h);
     transform: none;
     margin: 0;
     border: 0;

site/nostr-client.js

@@ -11,6 +11,20 @@
   const LOCALES = window.VoxVeraLocales || {};
   const FALLBACK_LANG = "en";
   const LANGUAGE_SELECT_IDS = ["topbar-lang", "field-lang", "viewer-lang"];
+  const PAPER_SELECT_IDS = ["topbar-paper", "viewer-paper"];
+  const PAPER_STORAGE_KEY = "voxvera_paper";
+  // Print paper sizes. `css` is the CSS @page size keyword. The actual sheet
+  // dimensions live in nostr-client.css (--sheet-w / --sheet-h per paper class).
+  const PAPER_SIZES = {
+    letter: { css: "Letter" },
+    a4: { css: "A4" }
+  };
+  const DEFAULT_PAPER = "letter";
+  // ISO 3166-1 alpha-2 regions whose default print paper is US Letter.
+  // Everywhere else defaults to A4 (ISO 216), which is the global standard.
+  const LETTER_REGIONS = new Set([
+    "US", "CA", "MX", "CL", "CO", "CR", "GT", "DO", "PH", "VE", "PA", "NI", "SV", "HN", "BO", "EC", "PR"
+  ]);
   const EVENT_KIND = 30078;
   // Per-script letter-spacing policy for flyer text. `letter-spacing` is not
   // script-neutral, so the flyer tightens tracking only where it is safe:
@@ -183,6 +197,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "تم الجلب",
       loading_content: "جارٍ تحميل المحتوى...",
       load_failed: "تعذّر تحميل هذا الملصق.",
+      paper_size: "حجم الورق",
+      paper_letter: "US Letter (8.5 × 11 بوصة)",
+      paper_a4: "A4 (210 × 297 مم)",
       config_copied: "تم نسخ الإعداد.",
       lookup_placeholder: "naddr أو معرف حدث أو note1 أو nevent1 أو رابط nostr:",
       event_reference_required: "أدخل naddr أو معرف حدث أو note1 أو nevent1.",
@@ -237,6 +254,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Abgerufen",
       loading_content: "Inhalt wird geladen...",
       load_failed: "Dieses Plakat konnte nicht geladen werden.",
+      paper_size: "Papierformat",
+      paper_letter: "US Letter (8,5 × 11 Zoll)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Konfiguration kopiert.",
       lookup_placeholder: "naddr, Event-ID, note1, nevent1 oder nostr:-URL",
       event_reference_required: "Geben Sie naddr, Event-ID, note1 oder nevent1 ein.",
@@ -291,6 +311,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Fetched",
       loading_content: "Loading content...",
       load_failed: "Could not load this flyer.",
+      paper_size: "Paper size",
+      paper_letter: "US Letter (8.5 × 11 in)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Config copied.",
       lookup_placeholder: "naddr, event id, note1, nevent1, or nostr: URL",
       event_reference_required: "Enter an naddr, event id, note1, or nevent1.",
@@ -346,6 +369,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Recuperado",
       loading_content: "Cargando contenido...",
       load_failed: "No se pudo cargar este cartel.",
+      paper_size: "Tamaño de papel",
+      paper_letter: "US Letter (8,5 × 11 in)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Configuración copiada.",
       lookup_placeholder: "naddr, ID de evento, note1, nevent1 o URL nostr:",
       event_reference_required: "Ingrese un naddr, ID de evento, note1 o nevent1.",
@@ -400,6 +426,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "دریافت شد",
       loading_content: "در حال بارگذاری محتوا...",
       load_failed: "بارگذاری این پوستر ممکن نشد.",
+      paper_size: "اندازه کاغذ",
+      paper_letter: "US Letter (8.5 × 11 اینچ)",
+      paper_a4: "A4 (210 × 297 میلی‌متر)",
       config_copied: "پیکربندی کپی شد.",
       lookup_placeholder: "naddr، شناسه رویداد، note1، nevent1 یا URL nostr:",
       event_reference_required: "یک naddr، شناسه رویداد، note1 یا nevent1 وارد کنید.",
@@ -454,6 +483,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Charge",
       loading_content: "Chargement du contenu...",
       load_failed: "Impossible de charger cette affiche.",
+      paper_size: "Format du papier",
+      paper_letter: "US Letter (8,5 × 11 po)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Configuration copiee.",
       lookup_placeholder: "naddr, ID d'evenement, note1, nevent1 ou URL nostr:",
       event_reference_required: "Saisissez un naddr, ID d'evenement, note1 ou nevent1.",
@@ -508,6 +540,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "נטען",
       loading_content: "טוען תוכן...",
       load_failed: "לא ניתן לטעון כרזה זו.",
+      paper_size: "גודל נייר",
+      paper_letter: "US Letter (8.5 × 11 אינץ׳)",
+      paper_a4: "A4 (210 × 297 מ״מ)",
       config_copied: "התצורה הועתקה.",
       lookup_placeholder: "naddr, מזהה אירוע, note1, nevent1 או כתובת nostr:",
       event_reference_required: "הזן naddr, מזהה אירוע, note1 או nevent1.",
@@ -562,6 +597,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "लाया गया",
       loading_content: "सामग्री लोड हो रही है...",
       load_failed: "यह पोस्टर लोड नहीं हो सका।",
+      paper_size: "कागज़ का आकार",
+      paper_letter: "US Letter (8.5 × 11 इंच)",
+      paper_a4: "A4 (210 × 297 मिमी)",
       config_copied: "कॉन्फिग कॉपी हुआ.",
       lookup_placeholder: "naddr, इवेंट ID, note1, nevent1, या nostr: URL",
       event_reference_required: "naddr, इवेंट ID, note1, या nevent1 दर्ज करें.",
@@ -616,6 +654,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "取得しました",
       loading_content: "コンテンツを読み込んでいます...",
       load_failed: "このちらしを読み込めませんでした。",
+      paper_size: "用紙サイズ",
+      paper_letter: "US レター (8.5 × 11 インチ)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "設定をコピーしました。",
       lookup_placeholder: "naddr、イベントID、note1、nevent1、または nostr: URL",
       event_reference_required: "naddr、イベントID、note1、またはnevent1を入力してください。",
@@ -670,6 +711,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Buscado",
       loading_content: "Carregando conteúdo...",
       load_failed: "Não foi possível carregar este panfleto.",
+      paper_size: "Tamanho do papel",
+      paper_letter: "US Letter (8,5 × 11 pol)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Configuracao copiada.",
       lookup_placeholder: "naddr, ID do evento, note1, nevent1 ou URL nostr:",
       event_reference_required: "Insira um naddr, ID do evento, note1 ou nevent1.",
@@ -724,6 +768,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Загружено",
       loading_content: "Загрузка содержимого...",
       load_failed: "Не удалось загрузить эту листовку.",
+      paper_size: "Размер бумаги",
+      paper_letter: "US Letter (8,5 × 11 дюйма)",
+      paper_a4: "A4 (210 × 297 мм)",
       config_copied: "Конфигурация скопирована.",
       lookup_placeholder: "naddr, ID события, note1, nevent1 или URL nostr:",
       event_reference_required: "Введите naddr, ID события, note1 или nevent1.",
@@ -778,6 +825,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Imepakuliwa",
       loading_content: "Inapakia maudhui...",
       load_failed: "Imeshindwa kupakia bango hili.",
+      paper_size: "Ukubwa wa karatasi",
+      paper_letter: "US Letter (8.5 × 11 inchi)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Usanidi umenakiliwa.",
       lookup_placeholder: "naddr, kitambulisho cha tukio, note1, nevent1 au URL ya nostr:",
       event_reference_required: "Weka naddr, kitambulisho cha tukio, note1 au nevent1.",
@@ -832,6 +882,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "Getirildi",
       loading_content: "İçerik yükleniyor...",
       load_failed: "Bu el ilanı yüklenemedi.",
+      paper_size: "Kağıt boyutu",
+      paper_letter: "US Letter (8,5 × 11 inç)",
+      paper_a4: "A4 (210 × 297 mm)",
       config_copied: "Yapılandırma kopyalandı.",
       lookup_placeholder: "naddr, olay ID, note1, nevent1 veya nostr: URL",
       event_reference_required: "Bir naddr, olay ID, note1 veya nevent1 girin.",
@@ -886,6 +939,9 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       fetched: "已获取",
       loading_content: "正在加载内容...",
       load_failed: "无法加载此传单。",
+      paper_size: "纸张大小",
+      paper_letter: "US Letter (8.5 × 11 英寸)",
+      paper_a4: "A4 (210 × 297 毫米)",
       config_copied: "配置已复制。",
       lookup_placeholder: "naddr、事件 ID、note1、nevent1 或 nostr: URL",
       event_reference_required: "请输入 naddr、事件 ID、note1 或 nevent1。",
@@ -1142,6 +1198,14 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       const select = el(selectId);
       if (select) select.value = selected;
     });
+    PAPER_SELECT_IDS.forEach((selectId) => {
+      const select = el(selectId);
+      if (!select) return;
+      select.setAttribute("aria-label", nostrLabel("paper_size", selected));
+      Array.from(select.options).forEach((opt) => {
+        opt.textContent = nostrLabel(`paper_${opt.value}`, selected);
+      });
+    });
   }
 
   function setDefaultText(lang) {
@@ -1149,8 +1213,10 @@ Join us in a revolution that values truth and transparency. Together, we can bui
     el("editor-relays").value = relayText;
     el("viewer-relays").value = relayText;
     populateLanguageOptions();
-    const defaultLang = supportedLang(lang || getStoredUiLang() || navigator.language.split("-")[0]);
+    populatePaperOptions();
+    const defaultLang = supportedLang(lang || getStoredUiLang() || preferredBrowserLang());
     applyFlyerDefaults(defaultLang);
+    applyPaperSize(getStoredPaper() || preferredPaperSize());
     Object.entries(EMPTY_OUTPUT_LABELS).forEach(([id, key]) => setEmptyOutput(id, key, defaultLang));
     setLocalizedText("publish-status", "idle", defaultLang);
     setLocalizedText("viewer-status", "idle", defaultLang);
@@ -1170,6 +1236,96 @@ Join us in a revolution that values truth and transparency. Together, we can bui
     }
   }
 
+  // Walk the browser's full ordered preference list (navigator.languages),
+  // not just the single top choice, and return the first base language we
+  // actually support. This honors a user's secondary preference (e.g. prefers
+  // Dutch, then German) instead of jumping straight to the English fallback.
+  function preferredBrowserLang() {
+    const list = (navigator.languages && navigator.languages.length)
+      ? navigator.languages
+      : [navigator.language || ""];
+    for (const tag of list) {
+      const base = String(tag || "").split("-")[0];
+      if (base && LOCALES[base]) return base;
+    }
+    return "";
+  }
+
+  function supportedPaper(paper) {
+    return PAPER_SIZES[paper] ? paper : DEFAULT_PAPER;
+  }
+
+  function getStoredPaper() {
+    try {
+      const stored = window.localStorage.getItem(PAPER_STORAGE_KEY);
+      return stored && PAPER_SIZES[stored] ? stored : "";
+    } catch (_) {
+      return "";
+    }
+  }
+
+  // "By location" without geolocation: read the region subtag of the browser's
+  // locale list (the "GB" in "en-GB") and pick the paper that country prints on.
+  // Same signal we use for language, no permission prompt. Falls back to
+  // DEFAULT_PAPER only when no locale carries a region at all.
+  function preferredPaperSize() {
+    const list = (navigator.languages && navigator.languages.length)
+      ? navigator.languages
+      : [navigator.language || ""];
+    for (const tag of list) {
+      const parts = String(tag || "").split("-");
+      const region = parts.length > 1 ? parts[parts.length - 1].toUpperCase() : "";
+      if (/^[A-Z]{2}$/.test(region)) {
+        return LETTER_REGIONS.has(region) ? "letter" : "a4";
+      }
+    }
+    return DEFAULT_PAPER;
+  }
+
+  function ensurePageSizeStyle() {
+    let style = document.getElementById("voxvera-page-size");
+    if (!style) {
+      style = document.createElement("style");
+      style.id = "voxvera-page-size";
+      document.head.appendChild(style);
+    }
+    return style;
+  }
+
+  // Paper size is a local print/view preference — it is never written into the
+  // Nostr event, so a flyer authored on Letter reprints on A4 for a European
+  // viewer without changing the source event.
+  function applyPaperSize(paper) {
+    const selected = supportedPaper(paper);
+    const root = document.documentElement;
+    root.classList.remove("paper-letter", "paper-a4");
+    root.classList.add(`paper-${selected}`);
+    // @page size cannot read CSS custom properties reliably across engines, so
+    // drive it from an injected stylesheet that we rewrite on each change.
+    ensurePageSizeStyle().textContent =
+      `@media print { @page { size: ${PAPER_SIZES[selected].css} portrait; margin: 0; } }`;
+    try {
+      window.localStorage.setItem(PAPER_STORAGE_KEY, selected);
+    } catch (_) {}
+    PAPER_SELECT_IDS.forEach((id) => {
+      const sel = el(id);
+      if (sel) sel.value = selected;
+    });
+    updatePreviewScale();
+  }
+
+  function populatePaperOptions() {
+    PAPER_SELECT_IDS.forEach((id) => {
+      const sel = el(id);
+      if (!sel || sel.options.length) return;
+      Object.keys(PAPER_SIZES).forEach((key) => {
+        const opt = document.createElement("option");
+        opt.value = key;
+        sel.appendChild(opt);
+      });
+    });
+  }
+
   function applyFlyerDefaults(lang) {
     const defaults = localeDefaults(lang);
     flyerSource = "default";
@@ -1934,7 +2090,7 @@ Join us in a revolution that values truth and transparency. Together, we can bui
   }
 
   document.addEventListener("DOMContentLoaded", () => {
-    setDefaultText(getStoredUiLang() || navigator.language.split("-")[0]);
+    setDefaultText();
     if (window.ResizeObserver) {
       new ResizeObserver(updatePreviewScale).observe(el("flyer-preview"));
     } else {
@@ -1968,6 +2124,12 @@ Join us in a revolution that values truth and transparency. Together, we can bui
       select.addEventListener("change", () => applyLanguageChange(select.value || FALLBACK_LANG));
     });
 
+    PAPER_SELECT_IDS.forEach((selectId) => {
+      const select = el(selectId);
+      if (!select) return;
+      select.addEventListener("change", () => applyPaperSize(select.value || DEFAULT_PAPER));
+    });
+
     TEXT_FIELD_IDS.forEach((fieldId) => {
       const field = el(fieldId);
       if (!field) return;