I'm trying to upload a large CSV file to an Amazon S3 bucket through the web console. The upload fails with messages saying "Upload failed" and "Networking error—check your internet connection and reload the page." The error details aren't providing anything useful. What should I check to diagnose and fix this?
3 Answers
Check the S3 bucket and IAM permissions too. The identity you’re using needs permission to upload objects, such as s3:PutObject, and the bucket policy, encryption settings, or organization restrictions may also deny the upload. The S3 or CloudTrail logs can provide a more specific reason than the console message.
A generic networking error can come from the browser, VPN, proxy, firewall, or an interrupted connection—not necessarily from AWS itself. Try another browser or network, disable extensions and VPN temporarily, refresh your credentials, and check whether the browser can reach the S3 endpoint. For a large file, the command-line interface or an S3-compatible transfer tool is usually more reliable than the web console.
First, test whether the problem is specific to this file. Try uploading a small file and a smaller copy of the CSV. If smaller files work, the issue is probably the browser upload, file size, or an unstable connection. Splitting the data into smaller files or using a tool that supports multipart uploads can help with large files.
I’m uploading through the Amazon S3 web console, and I haven’t yet tested whether smaller files or another network work.