Definition
Validation data
Validation data is data used to evaluate a trained model during development and tune non-learned choices such as thresholds, prompts, hyperparameters, or stopping decisions. It helps detect overfitting before the final independent test.
Last updated: 25 June 2026
Why it matters
It protects teams from believing a model works simply because it memorized or overfit the training examples.
Signals to watch
- It is separated from training examples
- It guides tuning decisions
- It checks overfitting before launch