Asp net core 3 1 can not download files larger then 300 mb server returns 0


ASP.NET is a popular programming language used for building web applications. It provides a framework for dynamic websites and web services. However, one common issue that developers face is the inability to download files larger than 300 MB in ASP.NET Core 3.1. This can be frustrating, especially when the server returns a 0 . In this article, we will explore possible solutions to this problem and provide examples to help you overcome this limitation.

Understanding the Issue

Before we dive into the solutions, let's first understand why ASP.NET Core 3.1 has downloading large files. By default, ASP.NET Core has a maximum request size limit of 30 MB. This means that any file larger than 30 MB will be rejected by the server, resulting in a 0 response.

1: Increasing the Maximum Request Size

To the download of larger files, we need to increase the maximum request size limit in ASP.NET Core 3.1. This can be done by modifying the configuration in the Startup.cs file of your project.

In the above code snippet, we are configuring the Kestrel server options to allow a maximum request body size of 300 MB (314572800 bytes). By setting this value, ASP.NET Core will now accept larger file downloads without returning a 0 response.

Solution 2: Chunked File Download

to overcome the limitation of downloading large files is to a chunked file download mechanism. This involves dividing the file into smaller chunks and downloading them sequentially.

public IActionResult DownloadLargeFile()
    string filePath = "path/to/large/file";
    long fileSize = new FileInfo(filePath).Length;

    Response..Add("Content-Disposition", "attachment; filename=largefile.txt");
    Response.Headers.Add("Content-Length", fileSize.ToString());

    using (FileStream fs = new FileStream(filePath, FileMode.Open))
        byte[] buffer = new byte[4096];
        int bytesRead;

        while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) > 0)
            Response.Body.Write(buffer, 0, bytesRead);

     new EmptyResult();

In the above code snippet, we are implementing a chunked file download mechanism. We first retrieve the file size and set the necessary response headers. Then, we read the file in chunks and write them to the response body. This allows the client to download the file in smaller parts, avoiding the limitation of downloading large files.


Downloading files larger than 300 MB in ASP.NET Core 3.1 can be challenging due to the default request size limit. However, by increasing the maximum request size or implementing a chunked file download mechanism, you can overcome this limitation. The solutions provided in this article should help you enable the download of larger files in your ASP.NET Core applications.

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