How to download an image with Python 3/Selenium if the URL begins with “blob:”?

When using one can see that the link to a recieved image may look like this:


If the link is copied in to an address window it will open up the image, however - if "blob" is left out - it will simply open a new web whatsapp window.

I am trying to download the image displayed by this link.

But using common techniques such as using request, or urllib.request or even BeautifulSoup always struggle at one point: The "blob" at the beginning of the url will throw an error.

These answers Download file from Blob URL with Python will trhow either the Error

URLError: <urlopen error unknown url type: blob>

or the Error

InvalidSchema: No connection adapters were found for 'blob:'

(using BeatufilSoup)

Using a native approach like:

import requests

url = ''
fileName = 'test.png'
req = requests.get(url)
file = open(fileName, 'wb')
for chunk in req.iter_content(100000):

Will simply result in the same error as using BeautifulSoup.

I am controlling Chrome using Selenium in Python, however I was unable to download the image correctly using the provided link.



A blob is a filelike object of raw data stored by the browser.

You can see them at chrome://blob-internals/

It's possible to get the content of a blob with Selenium with a script injection. However, you'll have to comply to the cross origin policy by running the script on the page/domain that created the blob:

def get_file_content_chrome(driver, uri):
  result = driver.execute_async_script("""
    var uri = arguments[0];
    var callback = arguments[1];
    var toBase64 = function(buffer){for(var r,n=new Uint8Array(buffer),t=n.length,a=new Uint8Array(4*Math.ceil(t/3)),i=new Uint8Array(64),o=0,c=0;64>c;++c)i[c]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".charCodeAt(c);for(c=0;t-t%3>c;c+=3,o+=4)r=n[c]<<16|n[c+1]<<8|n[c+2],a[o]=i[r>>18],a[o+1]=i[r>>12&63],a[o+2]=i[r>>6&63],a[o+3]=i[63&r];return t%3===1?(r=n[t-1],a[o]=i[r>>2],a[o+1]=i[r<<4&63],a[o+2]=61,a[o+3]=61):t%3===2&&(r=(n[t-2]<<8)+n[t-1],a[o]=i[r>>10],a[o+1]=i[r>>4&63],a[o+2]=i[r<<2&63],a[o+3]=61),new TextDecoder("ascii").decode(a)};
    var xhr = new XMLHttpRequest();
    xhr.responseType = 'arraybuffer';
    xhr.onload = function(){ callback(toBase64(xhr.response)) };
    xhr.onerror = function(){ callback(xhr.status) };'GET', uri);
    """, uri)
  if type(result) == int :
    raise Exception("Request failed with status %s" % result)
  return base64.b64decode(result)

bytes = get_file_content_chrome(driver, "blob:")

Blobs are not actual files to be remotely retrieved by a URI. Instead, they are programatically generated psuedo-URLs which are mapped to binary data in order to give the browser something to reference. I.e. there is no attribute of <img> to provide raw data so you instead create a blob address to map that data to the standard src attribute.

From the MDN page linked above:

The only way to read content from a Blob is to use a FileReader. The following code reads the content of a Blob as a typed array.

var reader = new FileReader();
reader.addEventListener("loadend", function() {
   // reader.result contains the contents of blob as a typed array

For people who are trying to do the same in node and selenium, please refer below.

var script = function (blobUrl) {
    var uri = arguments[0];
    var callback = arguments[arguments.length -?1];
    var toBase64 = function(buffer) {
        for(var r,n=new Uint8Array(buffer),t=n.length,a=new Uint8Array(4*Math.ceil(t/3)),i=new Uint8Array(64),o=0,c=0;64>c;++c)
            i[c]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".charCodeAt(c);for(c=0;t-t%3>c;c+=3,o+=4)r=n[c]<<16|n[c+1]<<8|n[c+2],a[o]=i[r>>18],a[o+1]=i[r>>12&63],a[o+2]=i[r>>6&63],a[o+3]=i[63&r];return t%3===1?(r=n[t-1],a[o]=i[r>>2],a[o+1]=i[r<<4&63],a[o+2]=61,a[o+3]=61):t%3===2&&(r=(n[t-2]<<8)+n[t-1],a[o]=i[r>>10],a[o+1]=i[r>>4&63],a[o+2]=i[r<<2&63],a[o+3]=61),new TextDecoder("ascii").decode(a)
    var xhr = new XMLHttpRequest();
    xhr.responseType = 'arraybuffer';
    xhr.onload = function(){ callback(toBase64(xhr.response)) };
    xhr.onerror = function(){ callback(xhr.status) };'GET', uri);
driver.executeAsyncScript(script, imgEleSrc).then((result) => {

For detailed explanation, please refer below link


Recent Questions

Top Questions

Home Tags Terms of Service Privacy Policy DMCA Contact Us

©2020 All rights reserved.