Decoder. plain-English AI glossary

Weight decay

● Core

Gently shrinking weights toward zero during training so the model stays simple and generalizes.

Think of it like

Like a tidy-desk rule that quietly clears clutter each day, keeping only what earns its place.

Example

Adding weight decay stops a model from letting a few weights grow huge to memorize training quirks.

How it actually works

Weight decay penalizes large weights, nudging all of them slightly toward zero each step, which discourages the model from fitting noise and improves generalization. It’s closely related to L2 regularization, though how it’s applied differs between plain Adam and AdamW. Set too high it underfits by over-simplifying; too low and it barely helps — it’s a standard, mild regularizer in almost every training recipe.

For product teams

A quiet guard against overfitting that’s in nearly every training recipe.

For engineers

Penalty shrinking weights toward zero (≈ L2); improves generalization, decoupled in AdamW.

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