nbdev1 Migration

How to change your nbdev1 repo to work with nbdev2

v3.3: Directive syntax updates

All directive spellings are now equivalent: #| default_exp: core, #| default_exp:core, and #| default_exp core mean the same thing (previously each directive worked with only one of the delimiters, and the wrong one failed silently). A value of true is the same as no value, so #| hide: true and #| hide are one directive. Existing notebooks need no changes. Directives can also be stored in cell metadata, as a dict under an nbdev key: {"nbdev": {"hide": "true", "eval": "false"}} behaves the same as writing #| hide and #| eval: false in the cell. Every metadata value must be a str, matching the comment form’s raw-text values: JSON true/false raise an error rather than silently differing from "true"/"false". Notebook-level directives such as default_exp can go in the notebook metadata the same way. If a directive appears both in metadata and as a comment, the comment wins.

There are breaking changes for extension authors only. nbdev.process.extract_directives is gone: read directives from a cell’s directives property, and use cell.remove_directives() to strip them from the source. The cell.directives_ dict has also changed shape: keys never include a trailing colon, and each value is the directive’s raw text rather than a list of whitespace-split tokens ('' for a bare directive), so directives_['eval:'] == ['false'] becomes directives_['eval'] == 'false'. Processor methods are unchanged: they still receive whitespace-split positional args.

nbdev-clean (and therefore the git and Jupyter save hooks) now also repairs structural problems by default, such as stray outputs attrs on markdown cells, so a previously-invalid notebook shows a one-time diff on its next clean (--repair false disables this). It also gains opt-in migration flags which the hooks never trigger: --dirs respells comment directives canonically, --to_meta/--to_comments move named directives between comments and cell metadata, and --nb_meta moves default_exp into notebook metadata.

nbdev-install-hooks now also registers a git diff driver, so git diff shows notebook changes cell by cell as small source diffs (see nbdev.diff). The merge and diff drivers install independently (--merge false/--diff false), and --globally defines them machine-wide in ~/.gitconfig and your global git attributes file instead of per repo. Both drivers are now named jupyternotebook, the name nbdime also uses, so a committed .gitattributes activates whichever notebook driver each collaborator has enabled; repos installed under the old nbdev-merge/nbdev-diff names keep working, and re-running nbdev-install-hooks moves them to the new name (the stale attribute lines are harmless, as the appended new ones win). The new nbdev-diff command renders the same output between any two refs without touching your git config.

🛑Jan 2026 Major Version Update – Breaking Change🛑

nbdev3 is here! As many of you have been requesting, configuration has moved from settings.ini to pyproject.toml, following modern Python packaging standards (PEP 621). Your project metadata now lives in the standard [project] section, while nbdev-specific settings go in [tool.nbdev].

Migrating from nbdev2: Run nbdev-migrate-config in your project root to automatically convert your settings.ini to pyproject.toml and update your GitHub Actions workflows to use nbdev3-compatible versions. Your existing notebooks and code don’t need any changes.

Status of this document: The rest of this doc describes migration from the very old nbdev1 to nbdev2, and is not likely to be relevant to most folks who haven’t been frozen in tundra for the last few years.

Nbdev2 - Initial setup

nbdev v2 is a new from-scratch rewrite of nbdev that’s not backwards compatible. This page describes the changes you need to make to upgrade your nbdev v1 repo to work with the new version. The steps shown here should work on macOS or Linux (including Windows WSL)

The biggest change is that nbdev2 uses Quarto to generate your website, whereas nbdev1 used nbconvert and jekyll. You can use all of Quarto’s features directly in nbdev, so checkout the Quarto website to see all the amazing functionality it supports.

If you’ve pinned nbdev in requirements.txt or pyproject.toml (e.g nbdev<2) remove the version pin. (If you don’t know what this means, then you don’t have it, so you can ignore this step).

Install the latest version of nbdev by typing:

pip install -U nbdev

or:

conda install -c fastai nbdev

You may need to restart your terminal for the new commands to be visible to your shell.

Upgrade directives

nbdev has slightly changed how “directive comments” like export and default_exp work, in order to align with how Quarto does things. Now, instead of just adding a # to the start to indicate a directive (e.g #export), you now need to use #| (e.g #| export). You can also optionally add a space (e.g #| export).

To automatically upgrade your directives to the new format, run in the root of your repo:

nbdev-migrate

You should now test that you can export your module by running:

nbdev-export

Note that nbdev-export replaces nbdev_build_lib. Run nbdev-export -h to see the options you can pass to it (normally you won’t need to pass any). To see a list of all the commands available in nbdev2, run nbdev-help.

Add and remove files

First set a variable with the name of your library, by running the following (replacing “yourlib” with the name of your library’s subdirectory)

export LIBNAME=yourlib

Now run the following:

git rm Makefile
git add $LIBNAME/_modidx.py
rm -rf docs
rm -f .gitconfig 
rm -f .git/hooks/post-merge

rm -f setup.py
curl -O https://raw.githubusercontent.com/fastai/nbdev3-template/master/styles.css
curl -O https://raw.githubusercontent.com/fastai/nbdev3-template/master/setup.py

cat >>.gitignore <<EOF
_docs/
_proc/
EOF

As you see above, we’ve remove the Makefile – that’s because all the things done by make before are now handled by nbdev commands directly.

Note

All documentation related files should be included in your nbs_path, and all paths should be relative to it. If you have set the nbs_path in your pyproject.toml, then copy your styles.css file inside of your nbs_path folder.

If you use GitHub Actions for continuous integration (CI) you can update this to use nbdev too as follows:

rm -f .github/workflows/main.yml
curl -O https://raw.githubusercontent.com/fastai/nbdev3-template/master/.github/workflows/test.yaml
curl -O https://raw.githubusercontent.com/fastai/nbdev3-template/master/.github/workflows/deploy.yaml
mv deploy.yaml test.yaml .github/workflows/

Update directive names

A number of directives have changed names. We’ll use perl to fix them. Run these lines in the root of your repo:

find . -name '*.ipynb' -exec perl -pi -e 's/#\|\s*hide_input/#| echo: false/' {} +
find . -name '*.ipynb' -exec perl -pi -e 's/#\|\s*hide_output/#| output: false/' {} +
find . -name '*.ipynb' -exec perl -pi -e 's/#\|\s*skip/#| eval: false/' {} +
find . -name '*.ipynb' -exec perl -pi -e 's/from nbdev.export import notebook2script/from nbdev import nbdev_export/' {} +
find . -name '*.ipynb' -exec perl -pi -e 's/notebook2script/nbdev_export/' {} +

These change the following directives to use functionality built into Quarto:

hide_input –> echo: false
hide_output –> output: false
skip –> eval: false

They also update the new location and name of the nbdev_export python function.

If you have any notebooks that you’ve asked nbdev1 to skip (using all_slow), you’ll need to add a raw cell to the top of your notebook containing YAML frontmatter. The frontmatter needs to include skip_showdoc: true to avoid running cells when rendering docs, and skip_exec: true to skip this notebook when running tests. E.g to do both, you would add a raw cell (or update your existing frontmatter raw cell) to contain:

---
skip_showdoc: true
skip_exec: true
---

Or you can also add these flags in a markdown cell,

# title
> description

- skip_showdoc: true
- skip_exec: true

Edit Workflow Permissions

Make sure your workflow permissions are set to “Read and write permissions”, which you can find in Settings → Actions → General → Workflow permissions:

Important

Failure to set the correct permissions may result in an error message like this:

 fatal: unable to access 'https://github.com/user/repo.git/': The requested URL returned error: 403
  Error: Action failed with "The process '/usr/bin/git' failed with exit code 128"

Edit GitHub Pages Permissions

At this point you will want to commit the files with the changes you made to GitHub. Wait for GitHub Actions to run and pass. A new branch in your repo will automatically be created called gh-pages. You want to enable GitHub Pages to work off this branch by configuring your Pages to settings to look like this:

Access this screen under Settings → Pages

Select “Deploy from a branch” in the drop down list for Source.
Specify gh-pages as the branch
Specify the /root as the location
Click save

Final steps

You should now edit pyproject.toml, and change doc_path from docs to _docs in [tool.nbdev], since that’s where nbdev2 will build your website.

If you use a custom domain for your website, you should move your CNAME file into the directory containing your notebooks.

Before pushing to GitHub, check that your website looks OK locally by running:

nbdev-preview

Now prepare to commit to GitHub:

nbdev-prepare

You can now commit to GitHub as usual. Finally, update Github Pages by clicking on the Settings tab in your repo, then click Pages on the left side bar. Set “Source” to gh-pages branch and the /root folder.