What is a .ipynb file?
application/x-ipynb+json
An IPYNB file is a Jupyter notebook: a JSON document holding an ordered list of cells and, unusually for a source file, the output each code cell produced. Markdown cells hold prose; code cells carry `source` as an array of lines, an `execution_count`, and an `outputs` array of stdout streams, result values, base64 images, and tracebacks, while `metadata.kernelspec` names the interpreter. The extension survives from the 2011 IPython Notebook, which became Project Jupyter in 2014.
How to use a .ipynb file
Use an example notebook to test nbformat parsers, nbconvert and jupytext, and diff tooling — checking that multi-line `source` arrays round-trip, that every output type including tracebacks and embedded images survives, and that a null `execution_count` reads as never-run rather than zero.