Simulating Bandwidth
by kirupa  |  4 October 2010

  Have questions? Discuss this Flash / ActionScript tutorial with others on the forums.

In the Creating a Preloader and Progress Bar tutorial, you learn about the always-interesting (yet puzzling) topic of preloaders. One of the challenges associated with creating preloaders is not just getting them to work, but actually proving to yourself that they work. That is actually a problem that you face in testing anything that requires simulating an active internet connection.

There are three big challenges:

  1. Most of you have fast internet connections, thus making any real testing of your preloaders an exercise in strobe photography.
  2. Your browser caches the Flash content, so even if you see the preloader once, you will have to clear your cache / temporary internet files before being able to see your preloader again.
  3. Testing locally doesn’t help because fetching content from your hard drive is usually faster than the fastest broadband available. If your content still lives online, you run into #1 where your high-speed internet connection fetches the content for you very quickly.

Fortunately, if you write Flash applications using the Flash IDE, you have a handy (but well hidden) feature that allows you to simulate your download speed to make testing your preloaders easy. Inside Flash, when you test our application by pressing Ctrl + Enter (Control | Test Movie), your application will display:

[ the default Flash Player window ]

When your application displays, it is being run locally with no download simulation going on. Now, the Flash Player that is currently displaying your application contains some nifty tricks up its sleeve. One such trick is allowing you to simulate the download. From this Player window, go to View | Simulate Download (or press Ctrl + Enter again):

[ simulate your download easily ]

This time, if your application is fairly large, notice that your application’s contents do not display immediately. If you happened to have a preloader specified, you get to see it as it is downloading your content:


[ your preloader is actually visible! ]

This is something that you didn’t see before! What is happening is that when you select the Simulate Download command, the Flash Player downloads your content at a speed that is set for you under View | Download Settings:

[ customize the simulated download speed easily ]

You can even set your own custom download speed via View | Download Settings | Customize. This allows you to easily test your application under various bandwidth constraints that you would otherwise not be able to do easily, so keep this little handy feature under your hat.

Getting Help

If you have questions, need some assistance on this topic, or just want to chat - post in the comments below or drop by our friendly forums (where you have a lot more formatting options) and post your question. There are a lot of knowledgeable and witty people who would be happy to help you out


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Kirupa Chinnathambi
I like to talk a lot - A WHOLE LOT. When I'm not talking, I've been known to write the occasional English word. You can learn more about me by going here.

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