Azure Blob always downloads when navigating to url

Question

In our application we give the user the abilty to upload a document to a windows azure blob storage account. After uploading the document or image it gets assigned some url (https://name.blob.core.windows.net/container/file-name.jpg). If the document is an image or a pdf or some file that can be rendered by the browser we are trying to display it in the browser without requiring the user to download the file. If we just open up a new window or tab and direct the user to the blob uri in IE, the image or pdf renders correctly in the browser. But, if we try to just open a new window pointing to the uri in Chrome, FireFox, or Safari, it just downloads the file instead of displaying it in the browser.

Is there a way to force the latter three browsers to just display the file instead of download it?

score 55 · Accepted Answer · answered Aug 04 '12 at 05:25

This is because you didn't set the content type property of the blob (the default is application/octet-stream, which triggers a download in most browsers). If you want PDF files to show correctly you'll need to change the content type of your PDF files to application/pdf (image/jpeg for jpeg files).

You can change the content type with common tools like Azure Storage Explorer, Cloud Storage Studio, CloudBerry, CloudXplorer, ... or by using the SDK. Note that some of these tools will automatically set the content type to the right one after uploading the file.

2

The url is no longer valid – spuder Mar 01 '17 at 18:08

score 28 · Answer 2 · edited May 23 '17 at 11:54

   blob.Properties.ContentType = "application/pdf";

//Get the content type of the file by extension

    public static string GetFileContentType(string FilePath)
    {
        string ContentType = String.Empty;
        string Extension = Path.GetExtension(FilePath).ToLower();

        switch (Extension)
        {
            case ConstantUtility.FILE_EXTENSION_PDF:
                ContentType = "application/pdf";
                break;
            case ConstantUtility.FILE_EXTENSION_TXT:
                ContentType = "text/plain";
                break;
            case ConstantUtility.FILE_EXTENSION_BMP:
                ContentType = "image/bmp";
                break;
            case ConstantUtility.FILE_EXTENSION_GIF:
                ContentType = "image/gif";
                break;
            case ConstantUtility.FILE_EXTENSION_PNG:
                ContentType = "image/png";
                break;
            case ConstantUtility.FILE_EXTENSION_JPG:
                ContentType = "image/jpeg";
                break;
            case ConstantUtility.FILE_EXTENSION_JPEG:
                ContentType = "image/jpeg";
                break;
            case ConstantUtility.FILE_EXTENSION_XLS:
                ContentType = "application/vnd.ms-excel";
                break;
            case ConstantUtility.FILE_EXTENSION_XLSX:
                ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
                break;
            case ConstantUtility.FILE_EXTENSION_CSV:
                ContentType = "text/csv";
                break;
            case ConstantUtility.FILE_EXTENSION_HTML:
                ContentType = "text/html";
                break;
            case ConstantUtility.FILE_EXTENSION_XML:
                ContentType = "text/xml";
                break;
            case ConstantUtility.FILE_EXTENSION_ZIP:
                ContentType = "application/zip";
                break;
            default:
                ContentType = "application/octet-stream";
                break;

        }


        return ContentType;
    }

Use this to set the content type of the blob while saving it.

Set Content-type of media files stored on Blob

if you use HttpPostedFileBase, it already contain content type attr ex: ``blockBlob.Properties.ContentType = httpPostedFileBase.ContentType;`` — user1686407, Jul 11 '16 at 03:42
That worked perfectly; I ended up settling on this to automatically determine the mime type for my file: `blob.Properties.ContentType = MimeMapping.GetMimeMapping(path);` — Lucent Fox, Feb 16 '17 at 16:26

score 2 · Answer 3 · answered Mar 19 '17 at 22:56

For those uploading files via PowerShell, use the below syntax to set content type during the upload.

Set-AzureStorageBlobContent -File <localFilePath> -Container <containerName> -Properties @{"ContentType"="text/plain"} -Context $ctx

Above I set the blob content type to text/plain, useful when uploading JSON and HTML files that will be used with templates. List of more content types header values here.

score 1 · Answer 4 · answered Jan 08 '20 at 15:07

If using the Azure SDK (12.x+) there is a change that requires the use of BlobHttpHeaders that pass in to the upload method (instead of blob.Properties.ContentType).

For example:

    var header = new BlobHttpHeaders();
    header.ContentType = "image/jpeg";

    var response = await blobClient.UploadAsync(stream, header);

Azure Blob always downloads when navigating to url

4 Answers4

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