Sure, here is how HTTP file upload works:

• The client (web browser) starts the file upload by submitting a form with the file to be uploaded.
• The form is submitted to the server, which then creates a new HTTP request with the file data as the body of the request.
• The server then sends the request to the web application, which processes the file data and stores it on the server.

The file upload process is typically done using the multipart/form-data content type. This content type allows the client to send multiple pieces of data in a single request, including the file data.

The file data is typically sent in chunks, with each chunk being a certain size. The server then reassembles the chunks into the original file.

The file upload process is typically done using the POST method. This method allows the client to send data to the server.

Here is an example of how to upload a file using HTTP:

<form action="upload.php" method="post" enctype="multipart/form-data">
  <input type="file" name="file">
  <input type="submit" value="Upload">
</form>

The action attribute of the form specifies the URL of the server-side script that will process the file upload. The enctype attribute specifies the content type of the form data. The file input element is used to select the file to be uploaded. The submit button is used to submit the form.

The server-side script that processes the file upload will typically do the following:

• Validate the file data to ensure that it is a valid file.
• Store the file on the server.
• Return a success message to the client.