Is it possible to save a Google Colaboratory Notebook to HTML?

Google Colab doesn't currently have such a feature as a built-in.

Your best route is to first download it through File > Download .ipynb and then use the standard tool for Jupyter Notebook conversion, nbconvert:

jupyter nbconvert --to html notebook.ipynb

If you use an Anaconda Python distribution, nbconvert is most likely already installed. If not, refer to what is described in their install instructions to be able to convert:

pip install nbconvert
# OR
conda install nbconvert

Method using only Google Colab

1. Download your .ipynb file

You can actually do it using only Google Colab. File -> Download .ipynb

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2. Reupload it so Colab can see it

Click on the Files icon on the far left:

Then Upload to session storage:

Select & upload your .ipynb file you just downloaded.

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3. Get your file's path

then obtain its path (you might need to hit the Refresh button before your file shows up):

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4. Conversion using %%shell

Then, just as in Julio's answer, execute in a Colab cell:

%%shell
jupyter nbconvert --to html /PATH/TO/YOUR/NOTEBOOKFILE.ipynb

The %%shell lets the interpreter know that the following script is interpreted as shell. Don't write anything before %%shell, use a distinct cell for this.

The form of /PATH/TO/YOUR/NOTEBOOKFILE.ipynb will be something like /content/lightaberration3.ipynb.

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5. Your file is ready

Might need to click Refresh again, but your notebook.html will appear in the files, so you can download it:

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The great thing about this is that nothing python-related has to be installed on your computer, not conda, not pip, only a browser.