Add Invisible IDs to Google Docs Paragraphs with Apps Script

🕵️‍♀️ Add Invisible IDs to Google Docs Paragraphs with Apps Script

July 11, 2025

Ever wanted to track paragraphs in a Google Doc without adding visible clutter? Whether you’re syncing content with an external system, managing edits across collaborators, or linking comments to specific sections, this technique lets you embed invisible unique IDs inside your document using zero-width characters. 🤯

Let’s dive into how this works, and how you can use it in your own Docs.

🧩 What problem does this solve?

Google Docs doesn’t let you attach custom metadata to paragraphs. So if you need to:

Track which paragraph was edited,
Sync content with a spreadsheet or database,
Leave comments linked to exact text blocks,
Reconstruct changes across versions…

…you’re stuck. Or at least, you were. Now, with this trick, we’ll inject an invisible UUID into each paragraph using a binary encoding made of zero-width characters (they’re 100% invisible to users).

Here’s the full script that:

Encodes data into invisible characters,
Inserts invisible UUIDs into each paragraph,
Lets you read or update those paragraphs later without breaking the IDs.

🔐 Encode any string into invisible characters

PrismJS Styled Code Block

JSCode.gs


function encodeToInvisible(input) {
  return input
    .split('')
    .map(char => {
      const binary = char.charCodeAt(0).toString(2).padStart(8, '0');
      return binary.replace(/0/g, '\u200B').replace(/1/g, '\u200C');
    })
    .join('');
}

🏷️ Assign invisible IDs to all paragraphs

Code.gs - Google Apps Script Example

JSCode.gs


function assignInvisibleIdsToParagraphs() {
  const body = DocumentApp.getActiveDocument().getBody();
  const paragraphs = body.getParagraphs();

  paragraphs.forEach((para) => {
    const text = para.getText();
    const clean = text.replace(/[\u200B\u200C]/g, '');
    if (clean.length !== text.length) return; // already has an invisible tag

    const uuid = Utilities.getUuid();
    const hidden = encodeToInvisible(uuid);
    para.insertText(0, hidden);
  });
}

🧼 Decode the invisible string back to readable text

decodeInvisible() – Code.gs

JSCode.gs


function decodeInvisible(encoded) {
  const binary = encoded
    .split('')
    .filter(c => c === '\u200B' || c === '\u200C')
    .map(c => c === '\u200B' ? '0' : '1')
    .join('');

  let output = '';
  for (let i = 0; i < binary.length; i += 8) {
    const byte = binary.slice(i, i + 8);
    if (byte.length < 8) break;
    output += String.fromCharCode(parseInt(byte, 2));
  }
  return output;
}

📜 Log all paragraph UUIDs to a Google Sheet

logInvisibleUUIDsInParagraphs()

JSCode.gs


function logInvisibleUUIDsInParagraphs() {
  const ss = SpreadsheetApp.openByUrl(YOUR_SS_URL);
  const sheet = ss.getSheets()[0];

  const body = DocumentApp.getActiveDocument().getBody();
  const paragraphs = body.getParagraphs();
  const rows = [];

  paragraphs.forEach((para, i) => {
    const text = para.getText();
    const hiddenPrefix = text.match(/^[\u200B\u200C]{8,}/);
    if (hiddenPrefix) {
      const decoded = decodeInvisible(hiddenPrefix[0]);
      rows.push([decoded, text]);
    }
  });

  sheet.getRange(2, 1, rows.length, rows[0].length).setValues(rows);
}

✏️ Edit a paragraph but preserve its hidden ID

replaceParagraphTextPreservingInvisibleId()

JSCode.gs


function replaceParagraphTextPreservingInvisibleId(para, newVisibleText) {
  const fullText = para.getText();
  const match = fullText.match(/^([\u200B\u200C]+)/);
  const invisiblePrefix = match ? match[1] : '';
  para.setText(invisiblePrefix + newVisibleText);
}

🔍 Get the invisible ID from the currently selected paragraph

getSelectedParagraphId()

JSCode.gs


function getSelectedParagraphId() {
  const doc = DocumentApp.getActiveDocument();
  const selection = doc.getSelection();
  if (!selection) return null;

  let element = selection.getRangeElements()[0]?.getElement();
  while (element && element.getType() !== DocumentApp.ElementType.PARAGRAPH) {
    element = element.getParent();
  }

  if (!element || element.getType() !== DocumentApp.ElementType.PARAGRAPH) return null;

  const text = element.getText();
  const match = text.match(/^([\u200B\u200C]{64,})/);
  return match ? decodeInvisible(match[1]) : null;
}

🧠 Use Cases

Document versioning: Reconstruct which paragraph was changed, even if content is edited.
Content sync: Link paragraphs to external datasets (Sheets, Firestore, Notion).
Inline moderation: Add moderation tags invisibly.
Semantic annotations: Track paragraph types (e.g., “question”, “summary”, “note”).

✅ You’re Ready!

You now have a reliable way to embed invisible, permanent IDs into your paragraphs. Use it to build smarter Docs automations or enhance content traceability, without adding a single visible character. 👻

Let me know if you’d like a follow-up on how to make these IDs clickable, extractable via UI, or synced in real time with Sheets!

⚖️ Comparison: Hidden ID vs Named Range

Google Sheets Embed Replica

Hidden IDs VS Named ranges