Google Colab “Unable to connect to runtime” – fixes & safe workflows

You open a Colab notebook and see “Unable to connect to the runtime” or it keeps trying to connect forever. This guide walks through practical fixes and ways to structure your work so disconnects don’t destroy your progress.

1. Check the basics

• Make sure your internet connection is stable (try another site).
• Open an incognito window and try a new blank Colab notebook.
• If new notebooks also fail → more likely a Colab / account / network issue.

2. Toggle runtime type & accelerator

Sometimes GPU/TPU runtimes become temporarily unavailable or buggy in certain regions. Switch between CPU / GPU / TPU to see if it fixes connection:

1. Runtime → Change runtime type.
2. Select “None” (CPU) and click Save.
3. If it works, try switching back to GPU later.

3. Clear browser & refresh

• Close other heavy tabs and extensions that may interfere with Colab.
• Hard refresh the notebook (Ctrl/Cmd + Shift + R).
• If needed, sign out of your Google account and sign back in.

4. Check for account or quota issues

Colab may throttle or restrict runtimes if:

• You’ve used a lot of GPU hours recently.
• You have many notebooks open at once.
• Your organization / network restricts certain connections.

Try:

• Closing all other Colab tabs.
• Waiting a few hours and trying again.
• Switching to another network (home vs office vs hotspot).

5. Design your workflow to survive disconnects

5.1 Keep code & data in Drive or Git, not just Colab

Always work from a folder in Drive or a Git repo, not just “Untitled0.ipynb” floating around.

5.2 Regularly save reproducible Capsules

When Colab is behaving, take snapshots so a bad runtime or environment update doesn’t cost you days of work. After a successful run:

from notebookcapsule import create_capsule

create_capsule(
    name="working-colab-state",
    notebook_path="/content/drive/MyDrive/projects/myproj/notebook.ipynb",
    data_dirs=["/content/drive/MyDrive/projects/myproj/data"],
    base_dir="/content/drive/MyDrive/projects/myproj",
)

Even if you can’t connect later, you have a Capsule in Drive with notebook + environment snapshot + data manifest.