Handling partial downloads with Google Drive API and CORS restrictions

Other Questions Google drive
1

Hey everyone, I’m stuck with a problem in my web app. I’m using Google Drive API to store and access large files. The thing is, I only need parts of these files most of the time, so I tried using the ‘Range’ header for partial downloads.

However, there’s an issue: when I make a CORS request, the Google API blocks the ‘Range’ header and only allows the ‘Authorization’ header. This means my browser cancels the GET request before it can execute.

// Example of a blocked request
fetch('https://drive.google.com/api/files/123', {
  headers: {
    'Authorization': 'Bearer token123',
    'Range': 'bytes=0-1000'
  }
})

I believe this could be a bug in their API. Has anyone found a workaround or a trick to avoid these preflight issues? Any ideas would be really appreciated!

2

have u tried using the google drive api’s fields parameter? it lets u specify which parts of the file u want. might work better than range headers. like this:

GET /drive/v3/files/fileId?fields=id,name,size

maybe that could help with partial data without cors issues?

3

I encountered a similar issue with partial downloads and found a workaround using a proxy. Instead of making the request directly from the browser, I set up a simple Node.js server using Express. The proxy receives the request from the client, adds the necessary Range header to call the Google Drive API, and then streams the partial content back to the web app. This method effectively bypasses the CORS restrictions, as the browser only communicates with the proxy server. It has served well in my projects, though careful error handling and authentication are important.

4

I’ve dealt with similar challenges when working with large files and APIs. One approach that’s worked well for me is implementing client-side chunking. Instead of relying on server-side range requests, you can break down the file into smaller chunks on the client side. This way, you’re making multiple standard requests for smaller portions of the file, which should bypass the CORS issues you’re experiencing with the Range header.

Here’s a basic pseudocode to illustrate:

async function downloadInChunks(fileId, chunkSize) {
  let offset = 0;
  const fileSize = await getFileSize(fileId);
  while (offset < fileSize) {
    const chunk = await downloadChunk(fileId, offset, chunkSize);
    processChunk(chunk);
    offset += chunkSize;
  }
}

This method requires more requests but avoids the CORS preflight issues. It’s worth noting that this approach may increase your API usage, so keep an eye on your quota limits.