Constrained decoding – Definition & Meaning

Definition of constrained decoding

: a generation technique that restricts which tokens a language model may choose at each decoding step so that the completed output satisfies a grammar, schema, vocabulary, or other specified constraint
- Constrained decoding prevented the model from emitting JSON that violated the application's schema.
- The code assistant used a grammar to remove syntactically impossible tokens before sampling the next token.

Origin & history

Constrained decoding has a long history in natural-language generation and machine translation. It became especially prominent with large language models in the early 2020s as developers used regular expressions, context-free grammars, and JSON schemas to obtain machine-readable outputs and valid tool calls.

Test yourself

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Related terms

structured output model output that follows a fixed, machine-readable format such as JSON with specific fields… sampling the way a model picks each next token from its list of possible choices, which decides how… token the basic unit of text a language model reads and writes: a whole word, part of a word, a… tokenizer the component that splits text into tokens before it goes into a model, and joins tokens back… function calling an API feature in which a model, instead of replying in plain text, outputs a structured… large language model a very large neural network trained on huge amounts of text to predict the next token, which…

Cite this entry

"Constrained decoding." AI Dictionary, Dadgogo, https://dadgogo.com/dictionary/constrained-decoding/. Accessed 8 Oct. 2026.