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Weights & Biases

proper nounAlso: W&B, wandb, W&B Weave

In plain wordsA company and online service that machine-learning teams use to log, chart and compare their training experiments, models and AI-app test results in shared dashboards.

  1. A commercial platform for experiment trackingexperiment tracking, n.: Keeping an automatic logbook of every model-training attempt — settings, data, code and results — so a team can compare attempts, repeat the good ones and see what changed. and model management, widely used in deep-learning research and industry, including at frontier AI laboratories. Its client library, wandb, logs hyperparameters, metrics, hardware statistics, media and outputs from training scripts to hosted or self-managed servers, where runs can be charted, compared and shared in collaborative reports. Further features include sweeps for hyperparameter searchhyperparameter tuning, n.: Trying out different settings for a model's training, such as learning speed or model size, and keeping the combination that performs best on data held back for checking., Artifacts for versioning datasets and models with their lineage, a model registrymodel registry, n.: A central catalog where a team stores every version of its trained models, with records of how each was made and which version is approved for use., and Weave, a toolkit for tracing and evaluating applications built on language modelslarge language model, n.: A computer program trained on enormous amounts of text to predict the words that come next. At vast scale, that simple skill lets it chat, answer questions, translate, summarize and write code.. The name alludes to the two kinds of learned parametersparameter, n.: One of the adjustable numbers inside an AI model that are tuned during training. Large language models have billions of them, and together they store what the model has learned. in a neural network, weightsweights, n.: The learned numbers inside a neural network that set how strongly each part influences the next. The finished set of weights is, in effect, the trained model itself. and biases.

    Everyone on the team posts loss curves to Weights & Biases, so we can see the moment a run diverges.

Origin

Founded in San Francisco in 2017 by Lukas Biewald, Chris Van Pelt and Shawn Lewis; Biewald and Van Pelt had earlier founded the data-labeling company CrowdFlower. Its experiment tracker spread quickly through deep-learning research from 2018, and the cloud-computing company CoreWeave, which announced the purchase in March 2025, acquired the firm that year.

Related

See also
  • experiment trackingexperiment tracking, n.: Keeping an automatic logbook of every model-training attempt — settings, data, code and results — so a team can compare attempts, repeat the good ones and see what changed.
  • MLflowMLflow, prop. n.: A free software platform that records machine-learning experiments, packages the resulting models and keeps track of which versions are ready to be used.
  • model registrymodel registry, n.: A central catalog where a team stores every version of its trained models, with records of how each was made and which version is approved for use.
  • hyperparameter tuninghyperparameter tuning, n.: Trying out different settings for a model's training, such as learning speed or model size, and keeping the combination that performs best on data held back for checking.
  • LLM observabilityLLM observability, n.: Recording and inspecting what an AI application actually did on each request — prompts sent, documents found, tools used, answers given, time and cost — so problems can be found and fixed.

Mentioned in

experiment trackingexperiment tracking, n.: Keeping an automatic logbook of every model-training attempt — settings, data, code and results — so a team can compare attempts, repeat the good ones and see what changed., model registrymodel registry, n.: A central catalog where a team stores every version of its trained models, with records of how each was made and which version is approved for use., MLflowMLflow, prop. n.: A free software platform that records machine-learning experiments, packages the resulting models and keeps track of which versions are ready to be used.