Frequently Asked Questions


What operating systems does Spell support?

The Spell CLI is based on Python runtime which runs on MacOS X, Linux, Windows, and all platforms that support Python.

What frameworks does Spell support?

Spell comes with PyTorch and TensorFlow 1 installed. You can use a different framework hosted in Docker using the --from command. Read more about using Docker containers in our docs.

What environments does Spell use?

Spell’s default environment includes:

  • Python 3
  • PyTorch and TensorFlow 1

If you would like to use a custom environment, you can include packages/dependencies using pip or conda. Read more about environments in our docs.

How much does it cost to use Spell if I'm on the Developer plan?

For the Developer plan, there are no monthly fees and no markups on hardware - you pay what we pay:

CPU Options

Machine TypevCPUsRAM (GB)Price$/hourPrice$/second
cpu (default)24FreeFree

Dedicated GPUs

Machine TypeNVIDIA GPUVRAM (GB)TFlopsvCPUsRAM (GB)Price$/hourPrice$/second
T41 x Tesla T416.08.1415$0.54$0.00015
K801 x Tesla K8012.04.3415$0.65$0.00018
P1001 x Tesla P10016.09.3415$1.66$0.00046
V1001 x Tesla V10016.015.7415$2.68$0.00074

Can Spell run my code on [my preferred] hardware?

Adding new types of hardware is easy. Email us at - we can probably accommodate you.

Can Spell run on premises for my organization?

Yes! Send us an e-mail at and let’s talk :)

How does Spell protect the data I upload?

For individuals using our public tiers, we store data privately in AWS (Amazon Web Services), and it’s never exposed to other users. Read more about using data on Spell in our docs.

For companies, we use your own storage/cloud infrastructure to make sure your data never leaves your system.

Can I mine cryptocurrency with Spell?

No, Spell does not allow cryptocurrency mining. Accounts that are used for cryptomining will be disabled.

Special Commands

What’s the difference between spell stop and spell kill?

spell stop stops execution of your run, but continues with saving outputs.
spell kill will stop all activity immediately and will not save any outputs.

Is there a way to access run output before the run completes?

Yes, you should be able to use spell ls and spell cp on a currently active run in much the same way that you use it for completed runs.

We are releasing new features requested by our users every day. Follow us on Twitter to find out when we release new features and commands.

Troubleshooting Your Run

Why do I get a “limit reached” error when trying my run?

Each plan has a different limit on the number of runs you can run concurrently. Check your plan limit on your settings page.

You can see how many runs you are currently running by checking spell ps.

Why is my run so slow?

Runs use CPU (Central Processing Unit) machine types by default. CPUs are a cost effective but slower method to run your code. Spell also offers GPU (Graphics Processing Unit) machine types which are faster. Read more about machine types in our docs.

To use a GPU machine, you need to specify the GPU type using the --machine-type or -t flag. To see a full list of available machine types, go to our pricing page.

You can see what machine type your run is using with spell ps. The machine type is listed in the final column on the right, K80 and V100 are both GPU machine types.

1 example1 python 0a2b3c4d Complete (0) -- 7 days ago CPU
2 example2 python 1b2c3d4e Complete (0) -- 7 days ago K80
3 example3 python 1a2c5d4f Complete (0) -- 7 days ago V100

Why don’t I see my run in spell ls?

spell ls only includes runs that have output files. If your run ended early, or if it did not save any files, then it will not show under spell ls. You will still be able to see the run under spell ps.

Also see: why was my run terminated?

Why was my run terminated?

If you are using your free credits, runs may be terminated if you do not have enough credits in your account for the full run.

Runs may also exit early if they encounter an error, which you can see with spell logs <run id>. You can find more about runs and how to find your run id in our docs.


How do I cancel my account?

Email us at and we can help you delete your account.

To uninstall the CLI tool, use pip uninstall spell.

What forms of payment do you accept?

We use Stripe to process payments. We accept all major credit and debit cards including Visa, MasterCard, American Express and Discover. We do not currently accept prepaid cards.

My payment was declined. What should I do?

Check you’re using an accepted credit or debit card (Visa, MasterCard, American Express and Discover). We use Stripe to process payments. If you’re still unable to add your credit card, contact us at

When will I be billed?

Billing occurs monthly and starts one month after your sign up date. You can check your billing period on your settings page or by using the spell status command.

Will I get billed if I kill my run?

Yes. We bill by time used, so you will still be billed if you kill your run or if your run fails.

Private Clusters

Why is machine start up so slow?

Check if the minimum machines for that machine type is set to 0. If so, it’s likely that the slow start up time is because Spell needs to bring up a new machine from scratch.

Check if you have any Additional Frameworks you have configured for that machine type. Try to only have the necessary frameworks you need. The fewer you have configured on a machine type, the faster Spell can bring up a new machine of that type from scratch.

Does the machine persist after the run is over?

We allow you some customization with regard to how available machine are.

By default “Minimum Machines” is set to 0, so we will terminate any machine when it is unused after it’s Idle Timeout has elapsed. You can set that higher if you want more availability - that will make a hello world run much faster. The tradeoff is that Amazon will charge you for that machine even when it’s Idle.

Another option is to set the 'Idle Timeout' which defaults to 30 minutes. This will mean that you have to wait for a machine to spin up for your first run but after that the machine will stay ready until the Idle Timeout has elapsed, so doing a new run on that same machine type within the Idle Timeout will be quick.

Why am I getting a no machines error?

Double check that the machine you are requesting is available within the region where your cluster is located. For example, US-West-1 on AWS does not have any GPUs.

Ensure your quota is high enough to allow for the machines you’re requesting. If not, you can request a higher quota from AWS or GCP.

You should also get an error message emailed to your Org Billing Admin if either of the above is the case which will help you troubleshoot the problem.

What machine types are available?

For a full list of available machine types, see our docs.

Do you support Preemtible (Spot) Instances?

Yes, we support Spot Instances in AWS and Preemptible Instances in GCP. In AWS, you need to increase your quota and have the role created for Spot Instances. They require different quotas and roles from the dedicated GPU machines of the same machine type.

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