Merriam-Webster vs Synonyms

Merriam-Webster's Dictionary API returns JSON definitions, pronunciations, and audio from the publisher's own Collegiate Dictionary and Thesaurus, plus specialized editions covering medical, learner's, Spanish-English, and grade-banded school dictionaries, each requiring a separate free API key. Keys are issued under a strict non-commercial license capped at 1,000 queries/day/key; using the service in a commercial product requires a separately negotiated agreement with Merriam-Webster.

The Synonyms API is STANDS4 Network's word-lookup service, returning synonym, antonym, and part-of-speech data for a submitted word as either JSON or XML from a single GET request against stands4.com's shared services endpoint — the same backend that powers sibling STANDS4 properties like Rhymes.com and Definitions.net. A live GET and OPTIONS preflight against that endpoint both echoed `access-control-allow-origin: *`; the service is free for up to 100 queries/day, with a paid commercial license available by contacting STANDS4 directly.