Base64 encoded image is not showing in gmail

base64 encoded images are not well supported in email. They aren't supported in most web email clients (including Gmail) and are completely blocked in Outlook. Apple Mail is one of the few clients that does support them, that's why you're able to see them there but not elsewhere.

Another thing to be mindful of with base64 encoded images is email file size. Gmail App (iOS, Android) and Outlook (iOS) truncate email messages whose file size exceeds 102KB. Remotely referenced images (Eg. <img src=""> do not count towards the email's file size, but base64 encoded images do and can quickly blow out an email's file size past the 102KB limit. Just something else to consider.

It looks like that direct encoded images (non-bease64 ) are also not supported by gmail :( - I write below snippet to convert image from base64 to direct form and send it in email - but still not see any image :( . To solve this issue you need to add images as attachements with cid and use that cid in img tags <img src="cid:123456"> - more details here

function convert() {
  let base64 = imageBase64.value.split('base64,')[1];
  let hex = [...atob(base64)].map(c => c.charCodeAt(0).toString(16).padStart(2, 0));
  let img = 'data:image/png,%' + hex.join('%');

  pic.src = img;
  msg.innerText = img;
Put your img base64 data uri here<br>
<button onclick="convert()">Convert</button><br> Result
<textarea id='msg' rows="4" cols="50"></textarea><br>
<img id='pic'>