Online simulator down?


The online simulator ( is currently down:

Screenshot 2020-12-09 at 12.13.29

Is this a temporary thing or has it been retired?

I wsas planning to use this for my teaching in the New Year due to online/remote learning…



It appears to be back online now. Phew!

The same thing has happened again this morning (25/01/21)…just as I prepare to give a live demo to my class. Fingers crossed it comes back in the next hour or I’m else going to end up looking stupid (as well as Arm tools looking unreliable to the students).

I really need to re-consider which platforms to use for teaching, reliability is a must.

it’s working for me!

Hi Craig,

The issues you have seen are likely related to large concurrent usage of the simulator. It’s not officially supported but we are aware how useful it can be for teaching at the moment, so we’ve just increased the resources available to it.

There were some similar discussions at the start of the pandemic which is why we’re keeping it up and running for now.

I’m interested to hear ideas for what you (and others in the Mbed community) would like from a simulator in the longer term? We don’t have plans to develop the existing simulator further, but there are other teams at Arm responsible for more powerful simulation tools who we could pass the feedback to.


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That’s great, many thanks for your support!

I’ve just been investigating the local install but unfortunately I can’t get the Docker version to work.

The simulator as is generally a good solution. More advanced tools are not generally really useful for introductory embedded systems courses. At this stage, we just want students to become proficient in C++ and be able to interface with basic peripherals.

My suggestion for the current simulator:

  • support for mutliple source files
  • add in a few more sensors/outputs etc.
  • attached to Mbed account to save source code

Also in general terms about software/platforms being used for educational purposes - installation needs to be (very!) simple. Anything involving running scripts or messing with paths leads to trouble! You end up having to spend large amounts of time helping students to install the tools on their own machines.

That is why I like online tools - they are cross-platform and no installation is required. But then we run into the issue of reliability. When they go down, it often leads to student dissatisfation and complaints, especially in the run up to a deadline!

So there is definitely a balance between online vs local install!

Many thanks,


Hi @JoeA

I’ve had some reports from students that the simulator was down at times in the last few days.

If you are seeing this occur regularly, would it be possible to increase the resources again?

The provided local install/Docker image just don’t seem to work, so we are relying on the online simulator.

We just need to get to May without any major disasters! The plan for the next academic year is to move to local Mbed Studio so everything will be ported over in summer. But until then, we are relying on the simulator!

Many thanks,


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