Free Dictionary vs Words

Free Dictionary API is a keyless REST service built and maintained by a solo developer, returning English word definitions, phonetic spellings, audio pronunciation clips, parts of speech, usage examples, and synonyms/antonyms as plain JSON from a single GET request. It now serves more than 10 million requests a month and is funded entirely through voluntary donations rather than any paid tier.

WordsAPI is a RapidAPI-hosted REST dictionary/thesaurus returning JSON definitions, synonyms, antonyms, rhymes, pronunciations, and word-frequency data across more than 150,000 English words — its own docs still show code samples calling the deprecated `wordsapiv1.p.mashape.com` host with an `X-Mashape-Key` header, but that legacy domain now refuses every request and a current RapidAPI key against the live `.p.rapidapi.com` proxy is required instead. A live unauthenticated request against that real proxy host returned a reflected `access-control-allow-origin` header plus `access-control-allow-credentials: true`, confirming CORS; its free tier covers 2,500 requests/day before paid plans starting at $10/month raise the ceiling to 25,000+/day.