What Is an IPYNB File?

The short answer

An `.ipynb` file is a JSON document used by Jupyter notebooks. The extension originated with IPython Notebook, but modern notebooks can use Python, R, Julia, and other kernels. It is a structured document, not a PDF and not an executable program by itself.

A notebook viewer can read the structure and show content that was saved with the file. It cannot reproduce a result that was never saved or safely run the code just because the code is present.

What the file can store

A typical notebook contains an ordered sequence of Markdown, code, and raw cells. Code cells can also contain execution counts and saved results such as standard output, error tracebacks, tables, plots, images, and rich display data.

This is why two notebooks with identical source code can look different when opened: one may include saved outputs from a prior run, while the other may have no saved output at all.

What to check before sharing

Review both source cells and saved output. Paths, tokens, query results, table rows, charts, and tracebacks can remain inside a notebook after you remove them from the visible code.

Use a local viewer or this converter when you only need to inspect saved content. Use Jupyter, VS Code, or Colab when you need to edit or run cells in an appropriate environment.

Notebook versions

Most current notebooks use nbformat 4, where cells are stored in a top-level `cells` array. Older nbformat 3 files commonly store cells under `worksheets`. This site recognizes both structures, but unsupported extensions and custom output types are shown with a clear limitation rather than executed.