Croissant 
¶
Croissant 🥐 is a high-level format building on schema.org for machine learning datasets that combines metadata, resource file descriptions, data structure, and default ML semantics into a single file. It works with existing datasets to make them easier to find, use, and support with tools.
Here, we demonstrate how LaminDB can be used to validate Croissant files:
# pip install lamindb
!lamin init --storage ./test-lamin-croissant
Show code cell output
→ initialized lamindb: anonymous/test-lamin-croissant
import lamindb as ln
import json
ln.track()
Show code cell output
→ connected lamindb: anonymous/test-lamin-croissant
→ created Transform('JrCl7M9EHpVm0000', key='croissant.ipynb'), started new Run('6RypAcsqgR0yYbal') at 2026-03-06 16:25:05 UTC
→ notebook imports: lamindb-core==2.3a2
• recommendation: to identify the notebook across renames, pass the uid: ln.track("JrCl7M9EHpVm")
croissant_path, dataset1_path = ln.examples.croissant.mini_immuno()
croissant_path
Show code cell output
/opt/hostedtoolcache/Python/3.13.12/x64/lib/python3.13/site-packages/anndata/_io/zarr.py:44: UserWarning: Writing zarr v2 data will no longer be the default in the next minor release. v3 data will be written by default. If you are explicitly setting this configuration, consider migrating to the zarr v3 file format.
f = open_write_group(store)
PosixPath('mini_immuno.anndata.zarr_metadata.json')
with open(croissant_path) as f:
dictionary = json.load(f)
print(json.dumps(dictionary, indent=2))
Show code cell output
{
"@context": {
"@vocab": "https://schema.org/",
"cr": "https://mlcommons.org/croissant/",
"ml": "http://ml-schema.org/",
"sc": "https://schema.org/",
"dct": "http://purl.org/dc/terms/",
"data": "https://mlcommons.org/croissant/data/",
"rai": "https://mlcommons.org/croissant/rai/",
"format": "https://mlcommons.org/croissant/format/",
"citeAs": "https://mlcommons.org/croissant/citeAs/",
"conformsTo": "https://mlcommons.org/croissant/conformsTo/",
"@language": "en",
"repeated": "https://mlcommons.org/croissant/repeated/",
"field": "https://mlcommons.org/croissant/field/",
"examples": "https://mlcommons.org/croissant/examples/",
"recordSet": "https://mlcommons.org/croissant/recordSet/",
"fileObject": "https://mlcommons.org/croissant/fileObject/",
"fileSet": "https://mlcommons.org/croissant/fileSet/",
"source": "https://mlcommons.org/croissant/source/",
"references": "https://mlcommons.org/croissant/references/",
"key": "https://mlcommons.org/croissant/key/",
"parentField": "https://mlcommons.org/croissant/parentField/",
"isLiveDataset": "https://mlcommons.org/croissant/isLiveDataset/",
"separator": "https://mlcommons.org/croissant/separator/",
"extract": "https://mlcommons.org/croissant/extract/",
"subField": "https://mlcommons.org/croissant/subField/",
"regex": "https://mlcommons.org/croissant/regex/",
"column": "https://mlcommons.org/croissant/column/",
"path": "https://mlcommons.org/croissant/path/",
"fileProperty": "https://mlcommons.org/croissant/fileProperty/",
"md5": "https://mlcommons.org/croissant/md5/",
"jsonPath": "https://mlcommons.org/croissant/jsonPath/",
"transform": "https://mlcommons.org/croissant/transform/",
"replace": "https://mlcommons.org/croissant/replace/",
"dataType": "https://mlcommons.org/croissant/dataType/",
"includes": "https://mlcommons.org/croissant/includes/",
"excludes": "https://mlcommons.org/croissant/excludes/"
},
"@type": "Dataset",
"name": "Mini immuno dataset",
"description": "A few samples from the immunology dataset",
"url": "https://lamin.ai/laminlabs/lamindata/artifact/tCUkRcaEjTjhtozp0000",
"creator": {
"@type": "Person",
"name": "falexwolf"
},
"dateCreated": "2025-07-16",
"cr:projectName": "Mini Immuno Project",
"datePublished": "2025-07-16",
"version": "1.0",
"license": "https://creativecommons.org/licenses/by/4.0/",
"citation": "Please cite this dataset as: mini immuno (2025)",
"encodingFormat": "zarr",
"distribution": [
{
"@type": "cr:FileSet",
"@id": "mini_immuno.anndata.zarr",
"containedIn": {
"@id": "directory"
},
"encodingFormat": "zarr"
}
],
"cr:recordSet": [
{
"@type": "cr:RecordSet",
"@id": "#samples",
"name": "samples",
"description": "my sample"
}
]
}
dataset1_path
Show code cell output
PosixPath('mini_immuno.anndata.zarr')
artifact = ln.integrations.curate_from_croissant(croissant_path)
Show code cell output
! calling anonymously, will miss private instances
! file path mini_immuno.anndata.zarr is not part of a known storage location, will be duplicated to: StorageSettings(root='/home/runner/work/lamin-mlops/lamin-mlops/docs/test-lamin-croissant', uid='si4NcORvhs8t')
Project label, license, description, version tag, and file paths are automatically extracted from the Croissant file. More metadata can be supported in the future.
artifact.describe()
Show code cell output
Artifact: mini_immuno.anndata.zarr (1.0) | description: Mini immuno dataset - A few samples from the immunology dataset ├── uid: gwsbqIaopdgDZBym0000 run: 6RypAcs (croissant.ipynb) │ kind: dataset otype: AnnData │ hash: N4_3ooEU3qkk97bWijn9XA size: 21.5 KB │ branch: main space: all │ created_at: 2026-03-06 16:25:07 UTC created_by: anonymous │ n_files: 95 ├── storage/path: │ /home/runner/work/lamin-mlops/lamin-mlops/docs/test-lamin-croissant/.lamindb/gwsbqIaopdgDZBym.anndata.zarr └── Labels └── .ulabels ULabel https://creativecommons.org/licenses/b… .projects Project Mini Immuno Project
ln.finish()
Show code cell output
→ finished Run('6RypAcsqgR0yYbal') after 2s at 2026-03-06 16:25:08 UTC