Descargar la transcripción de un vídeo de YouTube (texto, SRT o CSV)

// Responsive Muse · YouTube Transcript Downloader · v1.0 · 2026-10-23
// Saves the transcript of a YouTube video as plain text (handy to paste into ChatGPT, Claude or
// Gemini), text with timestamps, SRT subtitles or CSV. Works on any video that has a transcript
// (most do, auto-generated or not), in the language YouTube shows it. It opens the transcript
// panel itself. It makes no network requests of its own and never reads cookies, passwords or tokens.
(async () => {
  const TOOL = 'Descargar transcripción de YouTube';
  const FORMAT = 'txt';        // 'txt' (plain text), 'timestamps' (text with [mm:ss]), 'srt' (subtitles) or 'csv'

  const video = new URLSearchParams(location.search).get('v');
  if (location.hostname !== 'www.youtube.com' || !video) {
    alert('Abre primero el vídeo de YouTube, por ejemplo:\nhttps://www.youtube.com/watch?v=zjkBMFhNj_g');
    return;
  }
  // A small box on the page shows progress and asks before changing anything,
  // so you never need to read or edit the console.
  const many = (n, word) => `${n} ${n === 1 ? word : ({ canal: 'canales', 'canción': 'canciones', 'publicación': 'publicaciones', 'elemento guardado': 'elementos guardados' })[word] || word + 's'}`;   // 1 vídeo, 2 vídeos
  const panel = (() => {
    const box = document.createElement('div');
    box.style.cssText = 'position:fixed;right:16px;bottom:16px;z-index:2147483647;width:340px;max-width:calc(100vw - 32px);' +
      'background:#111318;color:#e6e8ee;font:14px/1.5 system-ui,sans-serif;border-radius:12px;padding:16px;' +
      'box-shadow:0 8px 30px rgba(0,0,0,.4);text-align:left';
    const head = document.createElement('strong');
    head.textContent = TOOL;
    const msg = document.createElement('p');
    msg.style.cssText = 'margin:8px 0 12px;white-space:pre-line';
    const row = document.createElement('div');
    row.style.cssText = 'display:flex;flex-wrap:wrap;gap:8px;justify-content:flex-end';
    box.append(head, msg, row);
    document.body.append(box);
    const button = (label, primary, onClick) => {
      const b = document.createElement('button');
      b.textContent = label;
      b.style.cssText = 'font:600 14px system-ui,sans-serif;padding:8px 14px;border-radius:8px;cursor:pointer;' +
        (primary ? 'background:#0f766e;color:#fff;border:1px solid #0f766e' : 'background:none;color:#e6e8ee;border:1px solid #3a3f4b');
      b.onclick = onClick;
      row.append(b);
    };
    return {
      text(t) { msg.textContent = t; },
      ask(t, yes) {
        msg.textContent = t;
        row.replaceChildren();
        return new Promise(r => {
          button('Cancelar', false, () => { row.replaceChildren(); r(false); });
          button(yes, true, () => { row.replaceChildren(); r(true); });
        });
      },
      stoppable(onStop) { row.replaceChildren(); button('Parar', false, onStop); },
      actions(t, list) {
        msg.textContent = t;
        row.replaceChildren();
        list.forEach(([label, primary, run]) => button(label, primary, run));
      },
      finish(t) { this.actions(t, [['Cerrar', true, () => box.remove()]]); },
      close() { box.remove(); },
    };
  })();
  // Offer the result as a downloaded file or as clipboard text (a real click, so it always works)
  const deliver = (summary, body, file) => {
    const save = () => {
      const a = document.createElement('a');
      a.href = URL.createObjectURL(new Blob([/\.csv$/.test(file) ? '\ufeff' + body : body], { type: 'text/plain;charset=utf-8' }));
      a.download = file;
      a.click();
      setTimeout(() => URL.revokeObjectURL(a.href), 5000);
      panel.text(`${summary}\nGuardado como ${file} (mira tu carpeta de Descargas).`);
    };
    const copy = () => navigator.clipboard.writeText(body)
      .then(() => panel.text(`${summary}\nCopiado. Pégalo en una hoja de cálculo o en una nota.`))
      .catch(() => panel.text(`${summary}\nEl navegador ha bloqueado el portapapeles: usa Descargar.`));
    panel.actions(summary, [['Cerrar', false, () => panel.close()], ['Copiar', false, copy], ['Descargar', true, save]]);
  };
  const sleep = ms => new Promise(r => setTimeout(r, ms));
  const clean = s => (s || '').replace(/\s+/g, ' ').trim();
  // New transcript panel (transcript-segment-view-model) and the old one (ytd-transcript-segment-renderer)
  const segments = () => document.querySelectorAll('transcript-segment-view-model, ytd-transcript-segment-renderer');

  // 1. Open the transcript panel (the "Show transcript" button in the description) and wait for it to fill
  document.querySelector('video')?.pause();
  if (!segments().length) {
    const open = document.querySelector('ytd-video-description-transcript-section-renderer button');
    if (!open) {
      panel.finish('Este vídeo no tiene transcripción (no hay botón «Mostrar transcripción» en la descripción). Prueba con otro vídeo.');
      return 0;
    }
    open.click();
  }
  panel.text('Abriendo la transcripción…');
  let n = 0;
  for (let i = 0, stable = 0; i < 40 && stable < 4; i++) {   // up to 20 s, until the count stops growing
    await sleep(500);
    const now = segments().length;
    stable = now && now === n ? stable + 1 : 0;
    n = now;
  }
  const rows = [...segments()].map(s => ({
    ts: clean((s.querySelector('[class$="SegmentViewModelTimestamp"], .segment-timestamp') || {}).textContent),
    text: clean((s.querySelector('.ytAttributedStringHost, .segment-text') || {}).textContent),
  })).filter(r => r.text);
  if (!rows.length) {
    panel.finish(n ? 'La transcripción está vacía o YouTube ha cambiado su diseño: avísanos en responsive-muse.com.'
      : 'La transcripción no se ha cargado. Recarga la página, espera a que empiece el vídeo y vuelve a ejecutar el script.');
    return 0;
  }

  // 2. Build the file and offer it
  const secs = ts => ts.split(':').reduce((a, v) => a * 60 + Number(v), 0);
  const srtTime = s => {
    const h = Math.floor(s / 3600), m = Math.floor(s / 60) % 60, sec = Math.floor(s % 60), ms = Math.round((s % 1) * 1000);
    return `${String(h).padStart(2, '0')}:${String(m).padStart(2, '0')}:${String(sec).padStart(2, '0')},${String(ms).padStart(3, '0')}`;
  };
  const end = document.querySelector('video')?.duration || secs(rows[rows.length - 1].ts) + 5;
  const cell = v => '"' + String(v).replace(/"/g, '""') + '"';
  const body = {
    txt: rows.map(r => r.text).join(' ').replace(/ {2,}/g, ' '),
    timestamps: rows.map(r => `[${r.ts}] ${r.text}`).join('\n'),
    srt: rows.map((r, i) => `${i + 1}\n${srtTime(secs(r.ts))} --> ${srtTime(i + 1 < rows.length ? secs(rows[i + 1].ts) : end)}\n${r.text}\n`).join('\n'),
    csv: ['Inicio,Segundos,Texto', ...rows.map(r => [r.ts, secs(r.ts), r.text].map(cell).join(','))].join('\n'),
  }[FORMAT] || rows.map(r => r.text).join(' ');
  const title = clean(document.querySelector('h1.ytd-watch-metadata, #title h1')?.textContent) || video;
  const ext = { txt: 'txt', timestamps: 'txt', srt: 'srt', csv: 'csv' }[FORMAT] || 'txt';
  const name = ('transcripcion-' + title).slice(0, 80).replace(/[\\/:*?"<>|]+/g, '_');
  const words = rows.map(r => r.text).join(' ').split(/\s+/).length;
  deliver(`Transcripción lista: ${rows.length} líneas, unas ${words.toLocaleString('es-ES')} palabras (hasta ${rows[rows.length - 1].ts}).`, body, `${name}.${ext}`);
  return rows.length;
})();