Decode Base64 Email with Apps Script

You can decode base64 encoded email messages in Gmail, or files in your Google Drive, using the base64Decode() method of Google Apps Script.

function base64DecodeEmail() {
  // If the base6f.txt file in Drive needs to be decoded
  var mime = DriveApp.getFilesByName('base64.txt').next().getBlob().getDataAsString();

  // If a Gmail message with subject base64 needs to be decoded
  var message ='subject:base64')[0].getMessages()[0];
  var mime = message.getRawContent();

  // Concatenate the chunks in the source
  mime = mime.replace(/\n|\r/g, '');

  // Extract the base64 string using regex
  var matches = mime.match(/base64[a-zA-Z0-9\+\/=]+/g);

  for (var line in matches) {
    var base64 = matches[line].replace(/^base64/, '');
    var decoded = Utilities.base64Decode(base64);
    var html = Utilities.newBlob(decoded).getDataAsString();
Amit Agarwal

Amit Agarwal

Google Developer Expert, Google Cloud Champion

Amit Agarwal is a Google Developer Expert in Google Workspace and Google Apps Script. He holds an engineering degree in Computer Science (I.I.T.) and is the first professional blogger in India.

Amit has developed several popular Google add-ons including Mail Merge for Gmail and Document Studio. Read more on Lifehacker and YourStory


Awards & Titles

Digital Inspiration has won several awards since it's launch in 2004.

Google Developer Expert

Google Developer Expert

Google awarded us the Google Developer Expert award recogizing our work in Google Workspace.

ProductHunt Golden Kitty

ProductHunt Golden Kitty

Our Gmail tool won the Lifehack of the Year award at ProductHunt Golden Kitty Awards in 2017.

Microsoft MVP Alumni

Microsoft MVP Alumni

Microsoft awarded us the Most Valuable Professional (MVP) title for 5 years in a row.

Google Cloud Champion

Google Cloud Champion

Google awarded us the Champion Innovator title recognizing our technical skill and expertise.

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