API reference

Neptune is joining OpenAI

Neptune has entered into a definitive agreement to be acquired by OpenAI, subject to closing conditions.

We will wind down the hosted (SaaS) service after a 3‑month transition period ending on March 4th, 2026. Self-hosted customers have been contacted by their account manager to work on a smooth transition path.

For information and instructions, visit the Transition Hub on the main documentation site.

•  Run

  ---

  Work with runs individually or in bulk.

  • neptune.init_run()
  • neptune.init_project()
  • Project.fetch_runs_table()
  • del run["namespace"]

•  management

  ---

  Manage your workspace and users.

  • invite_to_workspace()
  • create_project()
  • trash_objects()
  • clear_trash()

•  Field types

  ---

  A field is a location where metadata is logged. The field type determines the available methods and display options.

  • Artifact
  • File
  • FileSeries
  • FloatSeries
  • more →

•  Environment variables

  ---

  Use environment variables to make your setup more smooth and secure.

  • NEPTUNE_API_TOKEN
  • NEPTUNE_PROJECT
  • NEPTUNE_CUSTOM_RUN_ID
  • NEPTUNE_MODE
  • NEPTUNE_DATA_DIRECTORY
  • more →

•  Connection modes

  ---

  Set the logging and synchronization mode.

  • async (default)
  • debug
  • offline
  • read-only
  • sync

•  CLI

  ---

  You can use the Neptune Command Line Interface to manage and sync locally stored metadata.

  • neptune clear
  • neptune status
  • neptune sync

Browse the complete list of functions, parameters, and constants in the index →

Integrations

API references for Neptune integrations with other ML frameworks:

• Apache Airflow
• Catalyst
• Detectron2
• fastai
• Transformers
• Kedro
• Keras
• LightGBM
• Lightning
• MLflow
• Optuna
• Prophet
• PyTorch
• PyTorch Ignite
• Sacred
• scikit-learn
• skorch
• TensorBoard
• XGBoost

Errors, warnings, and other messages

For error help pages, expand the Erros and messages section in the left nav.

Other errors:

• Out of range float values are not JSON compliant → Downgrade simplejson to 3.18
• Connection pool is full, discarding connection: app.neptune.ai → Non-issue unrelated to Neptune.¹

See also

• NQL (Neptune Query Language) – used to construct complex queries when fetching runs.
• System namespace (sys) – contains the name, description, tags, creation time, and other auto-logged metadata.
• Change the location of the .neptune folder – see how to move the directory or access it from elsewhere in your system.
• Set up a Neptune error handling function
• Help ≫ Debugging options

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1. The error is shown by urllib3 to indicate that a connection is dropped after a request is completed. It doesn't imply data loss. For details, see StackOverflow . ↩