how to make a user restrict to download?

I know this question is silly.

But as per our intelligent Client request, I am not able to answer his question. Any one help for this.

We are building a online tutoring site. where it contains pdf, .ppt, .doc formats files are uploaded for reading as course materials. His (Client) request is 开发者_Python百科that user can read all the contents but they must not download the materials and use this.

That is all the documents must be opened in their browsers.

Is it possible? Any other ideas?

Any other ideas?

Explain to your client that the only way for a document to appear on a user's computer screen is for the document to exist on that user's computer.

In other words, viewing a document involves downloading it. Even supposing the software on the user's computer somehow makes it impossible for the user to directly manipulate an electronic copy of the material, the user can take out a digital camera and take a picture of the screen.

There are ways to make it difficult for the user to save a copy of the file. However, it's likely that this will do more harm (frustrating users) than good (preventing theft).

Some users may want to peruse the material at times when they do not have an internet connection, or may want to copy it onto their mobile device (for instance), but accessing the internet on their mobile device is expensive so they would like to do the download on their computer.

If you send the data to the client the client has effectively downloaded it. You can make this difficult, but not impossible.

The only sure way to prevent downloading is to prevent viewing.

If this is a copyright problem it should be solved with legalese, not software.

Here are some guide-lines you may consider:

1. Don't put direct link of files such as:

   <a href="mydoc.pdf">Download</a>
   

Instead, try to generate your pdf dynamically or put a another encrypted medium for downloading eg:

<a href="download.php?file_id=1111111">Download</a>

2: Don't allow directory browsing, use htaccess file with following commands:

 Deny from ALL

3: Not sure, but you may possibly allow file opening this way too:

$filename="/path/to/file.jpg"; //<-- specify the image  file
if(file_exists($filename)){ 
 header('Content-Length: '.filesize($filename])); //<-- sends filesize header
 header('Content-Type: image/jpg'); //<-- send mime-type header
 header('Content-Disposition: inline; filename="'.$filename.'";'); //<-- sends filename     header
 readfile($filename); //<--reads and outputs the file onto the output buffer

 exit; //and exit
}

Note: above is just an example of image not pdf but you can modify it for your needs.

An online site does not necessarily mean it is a web site. You could write a custom client that accesses the data and displays it.

The data would need to be encrypted between the client and the server. It probably should not be sent 'in bulk' either.

The effort associated with developing that is prohibitive.

You could license the software that allows users to read books, page by page, that is part of the Safari Books Online web site.

As best I can tell, they take the pages that they are going to display and turn them into small images. These images look as if they are sent in a random order, and assembled by the browser via javascript.

These tactics won't stop a determined person from getting your clients content... but the effort is unlikely to be worth it.

You could put the docs into Google docs and embed the docs viewer into your site. Of course, there's no stopping people from taking screenshots, copy/pasting text, downloading HTML, etc.

What do you mean by "read" but not "download"?? Do you know that even if you disable cache (which by itself is a bad idea) won't restrict an eaaaasy right-click>view source, "save target as", etc.?

I mean, the best you can have is a flash reader that is harder to save the content from, and that means disabling selection and copying, but anyway, it doesn't forbid anything.

The only way to forbid download is to return HTTP 403 :)