Datamuse

About Datamuse

Datamuse is a word-finding query engine API for developers, offering a read-only HTTP/HTTPS service that returns words and multiword expressions matching a given set of constraints. Queries can combine constraints on meaning (words related to a given word or phrase), sound (words that sound like a given string), and spelling (similarity or wildcard patterns), along with predefined lexical relations such as synonyms, antonyms, homophones, and common noun-adjective pairings drawn from sources including WordNet and Google Books Ngrams. Context hints (topic words, left/right context) can be supplied to influence result ordering, and optional metadata flags add definitions, parts of speech, syllable counts, and pronunciation to results.

The default vocabulary covers roughly 550,000 English words and multiword expressions, with an additional Spanish-language vocabulary of about 500,000 terms drawn from books; custom vocabularies can be arranged by contacting the provider. Two endpoints are available: /words for constraint-based queries and /sug, intended as a backend for autocomplete on search input fields.

The API is aimed at developers building features such as autocomplete on text input fields, search relevancy ranking, assistive writing tools, and word games. It has been offered free to developers for over a decade; starting January 1, 2027, an API key will be required for all requests, with access limited to 100,000 requests per day per key.

Key features

• Find words matching constraints on meaning, spelling, sound, and vocabulary
• Word-relation queries (synonyms, antonyms, rhymes, related adjectives/nouns) via rel_[code] parameters
• Autocomplete suggestions via the /sug endpoint
• Metadata flags for definitions, parts of speech, syllable counts, and pronunciation
• Context-aware ranking using topic words and left/right context hints
• Support for an English vocabulary and a Spanish-language vocabulary

Frequently asked questions