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Hal Snyder edited this page Nov 16, 2018 · 168 revisions

General and Miscellaneous Questions

This is a place for questions that do not fit on any of our topical FAQ/Help pages, which you can find on the FAQ/Help portal.

Remember: if you don't find what you need, or if you'd like to ask a question, then please email at any time. We'd love to hear from you! Please include a link (the URL address in your browser) to any relevant project or document, as part of your email.

List of Questions:

Question: What tools are available for course management?

See the tutorial for anyone wanting to use CoCalc for teaching.

There is also an entire FAQ dedicated to Course management.

Question: How can I use Python3 by default in Sage worksheets?

First, try putting this in a cell of a Sage worksheet:

%default_mode python3

Then the rest of that worksheet will use Python3.

If you make a sage worksheet called


with the above content, it'll be used by default whenever you open a new worksheet in that project. You can create the above file quickly by navigating to your home directory in the file browser, then pasting the above in filename search in the upper left.

Question: I created an ssh key in my project; how do I easily copy it?

If you type ssh-keygen in a terminal, then you'll generate an ssh key, which you might use with github (say) or sage's trac to easily push and pull to repositories. To copy this ssh key, you could type cat .ssh/ and copy in the terminal, but you'll have to manually delete a bunch of newlines. Alternatively, do the following:

  1. In the project file list, click on the icon that looks like an eye in the middle on the right side of the screen to reveal hidden files (those that start with a dot).

  2. Click on the .ssh directory -- you can easily find it by typing "ssh" in the search box labeled "choose files..." on the left.

  3. Click on, then highlight everything and copy as usual.

  4. Click the eye again to turn off viewing hidden files.

Alternatively, type this into the small "terminal command" box in "files": cat ~/.ssh/*.pub. Below the box, you can conveniently copy/paste it!

You can also type the following into a full terminal: open ~/.ssh/

Question: How can I download a whole directory?

There is currently no provision to download an entire directory. To accomplish this, you can easily create a .zip-archive. Above the files view, on the right, there is a command-box. For a directory called "My Homework", type in:

zip "My Homework"

The directory name needs to be exactly the same, including upper and lowercase letters, and any space characters need to be protected by quoting the entire name.

If successful, a new file should appear.

Question: Can I pay with Paypal?

YES The only restriction is that because it is a manual process, at this time, we can accept only paypal for course subscriptions and 1-year subscriptions.

E-mail to set this up.

If I have a license for proprietary software, can I run it in a CoCalc project?

CoCalc runs on virtual computers in Google Compute Engine (Google’s cloud), on Ubuntu Linux. If you have a valid license to run software, it may be possible to install and run it on CoCalc.

How can I clear the scrollback buffer in a terminal without deleting the terminal?

In a "plain" terminal, type in "reset". That's command tells the terminal to reinitialize itself. This should clear the buffer, too.

If you use tmux or another multiplexer, it sits on top of that terminal interface. There, you run "reset" and then close and reopen the terminal tab.

In both cases, the terminal file, the session and chat is still there and you didn't lose any history.

CoCalc keeps saying that my clock is off. What should I do?

Here are some things to try:

  • Check system time on your computer and make sure it matches correct time for your timezone.
  • If you recently moved to a different timezone, check whether you have set your computer's clock manually rather than automatically detecting your current timezone. Try setting your computer to automatically connect to a time server.
  • Restart your web browser.
  • Try a different web browser.
  • Reboot your computer.

If none of the above helps, visit this link: and take a screenshot of all the "Date and Time Information" output. Then email the screenshot to along with the following information:

  • your computer's operating system name and version
  • browser name and version
  • city where you are connecting from.

I created an account with the same email used to invite me to collaborate on a project. However, when I follow the link to open the project, I get the following message, "Showing only public files".

Invitations expire after 14 days. Ask the project owner to invite you again.

Is it possible to nest cells in a CoCalc document (e.g., a sagews)?

It's not. HOWEVER, it is at least possible to have several different sagews files and easily link between them using markdown links. E.g., to link to a.sagews, do this:



Can I split the CoCalc browser tab to view two files, and not just two views of the same file?

This is not currently possible, except by opening two browser tabs. That said, we are working on adding this functionality, and it will be coming soon.

How long can a project be idle before it is sent to long term storage?

The current setting is for idle projects to be archived after 31 days. That number could change, as needed.

What if my question isn't answered above?

Email with lots of details about your question. Do not hesitate to immediately email us, because we are eager to hear from you!


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