Every time a video/audio streaming starts the Internet Download Manager (IDM) feels that there is a multimedia content on the page and allows you to download that multimedia content.
I don't think it's possible to prevent IDM from grabbing video/audio but is there a way to fool IDM to get a wrong video instead or make it very hard for IDM to guess which is the real video/audio playing?
EDIT: Actually My Question was from the server side point of view not the client running an IDM. So i guess the misunderstanding here is my fault. Many good answers here but not the one i was looking for
You need to open "Options->General" IDM dialog and press "Edit" near "Customize IDM download panels in browsers".
Then enable "Don't start downloading from web-players automatically" option (arrow 1 on the image) and press "OK" (arrow 2 on the image).
source: http://www.internetdownloadmanager.com/register/new_faq/video14.html
You can prevent IDM from starting the download using two ways,
The first way is by specifying file types that IDM should automatically grip, so you can exclude the certain file type, for instance "MP3" or "MP4". To do that configuration, you have to click on "Downloads" menu in the IDM's main GUI, and then select "Options", a new small window will appear, choose "File types" tab from it. Now in the first text input box you can add or remove the file types you want
The second way is by specifying certain sites that IDM shouldn't automatically download from them. You can find an input text box below the text box in the previous way which you can use for that purpose. for example you can add something like this: dropbox.com to prevent any automatic download from Dropbox site
Note:
- In the first way, you can enforce IDM to download from a specific link when its targets file type is not listed on the list of automatic grabbing types. to do that you should first click on "Keys..." button which is located in the "General" tab in the "Option" window, and from the window that will appear, make a tick in the second choice which will allow you specify a certain key that could be held while clicking on the desired link in order to enforce the IDM to start the Download
You need to open Options->General IDM dialog and press Edit near Customize IDM download panels in browsers.
Then enable Don't start downloading from web-players automatically option (arrow 1 on the image) and press OK.
You can stop automatic capturing from browser by going to Options > General and uncheck the browser you are currently using this will prevent any download from starting automatically
If you want to temporary disable IDM for single download you may hold Alt button while clicking on the download link to prevent IDM from taking the download.
You can press Alt key while downloading file.
来源：https://stackoverflow.com/questions/12802862/how-to-stop-idm-from-grabbing-video-audio