De MonsterDebugger is an open source debugger for Adobe Flash, Flex and AIR. De MonsterDebugger is made in Flex and AIR by design studio De Monsters.

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About Monster Debugger

Monster Debugger is a free and open source application created by De Monsters. The first version of the Monster Debugger was created purely for internal use and helped us considerably with the creation of various Flash projects. Although the first version was never released to the public at that time, we knew that a lot of people could benefit from the application so we set out to create a new optimized version which was released as version 2.0 in February 2009.

Monster Debugger 2.0 was a huge success and we iterated on the application quite a bit and even received some very nice contributions form other developers. Overall this version has been downloaded more than 56.000 times, something we never expected to happen! But we had more ideas and started working on version 3.0 at the end of 2009.

Version 3.0 of the Monster Debugger boasts some very nice new features and can support an even wider range of debugging needs than previous versions. Besides that it also features a completely redesigned interface and we also included a game as an alternative to those boring tutorials you usually find online.

About us Monsters

De Monsters is a digital creative agency from Amsterdam. Since 2007 we create interactive products, both online and offline. We do this for humans but also for ourselves. Highly inspired by Maurice Sendak's "Where the wild things are" we wear our Monster suits with pride. With our suits on we leave behind our human weaknesses and biases, making sure we are able to overcome any obstacle and face all problems thrown at us.

"So what does it mean to be a Monster?", you might ask. For Monsters it is a combination of things. Besides the usual Monster traits such as being able to roar and scaring someone every once in a while, a true Monster in this pack is passionate about creating interactive products with the user in mind. Observing and getting to know the users of our products is a constant factor in the Monster workflow so we can design and develop the best possible user experience. We like Adobe Flash & AIR, C++, HTML, Ruby and many other development tools to turn the created designs into fully working products. All Monsters have a diverse background which makes it possible to take on a diverse range of products, a thing we are proud of.

We are the Monsters, GRAW!

The team behind Monster Debugger

Paul Reijnierse

Founder, Managing Director

Paul, the blue Monster, is in many ways the public face of the Monsters. Although some Monsters think this is because of his almost flawless English, being raised by two English teachers and a having passion for American sports. Reality is that Paul knows most about the things that are going on in our cave.

You might have noticed that the blue Monster only has one eye. It wasn't always like that. When Paul was a toddler Monster he used both Monster eyes all the time. Having a keen sense of focus and knowing the importance of adapting and staying flexible he decided it would work a lot better only having one. This Monster evolution resulted in allowing all the other Monsters to wander off on their own creative workflow while we know that we can trust on Paul to keep everything flowing into the right direction. Adding the fact that Paul has a background as a developer and interaction designer he is the perfect partner when it comes to managing project expectations.

Erik van de Wiel

Founder, Creative Director

When the Vikings started to use the name Erik, they must've had this orange Monster in mind. Because Erik means "Lone Ruler". Sitting on his high throne, shouting his design commands down to the other Monsters, sometimes Erik sure does feel like he is the lone ruler of the Monsters. While all Monsters know better, there is some truth in it. In the end the Monsters are design driven, and since Erik is calling the shots when it comes to design, he does rule the Monsters in that respect.

Thankfully Erik doesn't need to unleash his Monstrous wrath very often. His passion for user experience goes deep and it is shared by the other Monsters, keeping them on the same path during all projects. Still, Erik pushes everyone on a day to day basis to create the best experience possible. He is a strong advocate of Goal Directed design and leads the Monster tribe when it comes to Interaction Design, Interface Design and Visual Design.

Ferdi Koomen

Partner, Lead Developer

The green Monster, Ferdi, completes the original team. But as his color reveals, his responsibilities lie somewhere totally different than those of the blue or orange Monsters. You see, green Monsters have a tendency to focus on the beauty of code. They create what the other Monsters design, and Ferdi has matured into a one of a kind developer who does it all: ActionScript 3, AIR, C++, iPhone, Android, web. You name it and Ferdi probably knows how to deal with it and if not he will create apps like Monster Debugger to figure out what's wrong.

But as with most Monsters, Ferdi can change his suit to a different color when the occasion calls for it. Just as his loyal pack of other green Monsters, Ferdi has a great eye for design as well. In fact, his background stretches all the way to the stone age of design: print. And since he still is an Interaction Designer at heart, you can be sure that his creations are always focused on the best user experience.

Joost Harts


Joost is the first human that joined the Monsters after Ferdi started his new green Monsters pack before we actually had the chance to put any vacancies up. He tried to seduce us by acting that he was intern material while he was actually trying to blow us away with his Flash, AIR, Android, Ruby and design skills. We agreed it would be best not to squeeze him into a small intern Monster suit and give him his own. Joost has English roots and because of that he is able to talk really funny. He also likes to cuddle furry animals at the animal shelter where he volunteers on the weekends and scare a few sharks when he is standing and roaring on his surfboard.

Stijn van der Laan


Stijn, the third human ever to receive a green Monster suit joined the Monsters after we got to know him while he was helping us empty a bottle of rum at our new office. Any human acting like a crazy sailor while loving Flash, iPhone, iPad and javascript is one of the good guys in a world of Monsters. Shortly after installing his Mac we noticed that he only listens to songs with a BPM way over 200. This started making sense after we learned that during the weekends Stijn is an underground hardcore DJ in Amsterdam. While the other Monsters usually utilize their super powers from Monday to Friday, the pictures of Stijn proves he definitely claim using them during the weekend as well.

Joeri Lefevre


Every team needs a crazy designer, we have Joeri. Joeri is: a game designer, illustrator, concept artist, an art teacher and currently busy to become the next Rembrandt in fine arts. Because of this busy life Joeri is able to wear his Monster suit about once a week. We got to know Joeri during his graduation year. Paul had the pleasure of working together with Joeri and create a cow slaughtering simulation game for veterinarians in training. Even though this sounds really gross, the result of the 3D world and cow, which Joeri made, are awesome! And if you ever see Joeri wearing a large mustache be sure to compliment him on this, it's something he is very proud of.

Suit up and become a Monster

We've got internships available. If you like the way we work and feel that you have a Monster hidden inside you, make sure you give us a roar. After all, it would be a shame to keep it hidden away.

Tree structure

Tree structure, lets you walk through your entire application on code-level

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Live editing

Live editing, means you can edit properties and instantly see the effects in your application

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Easy traces

Detailed traces, lets you trace Strings, Numbers, XML, Arrays, Objects with great detail

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Function testing

Method testing, is very easy as you can run most methods and catch the results instantly

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How it works

How it works, install De MonsterDebugger, import AS3 class, add any traces, start debugging

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Open source

Open source, is the way De Monsters are releasing this application, you can use it for free

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Download MonsterDebugger version 2.5.1 (examples included)

If you share our ambition for clean coding and easier debugging please help us by spreading the word.