3 Services from physics.openverbs.com

Looks up a single CODATA 2018 physical constant by its key, symbol, or exact name, returning its value, unit, uncertainty, and category.

Search physical constants by key, symbol, or name substring with ranked results (exact > prefix > substring matches)

Lists all physical constants in the dataset, optionally filtered by category (universal, adopted, electromagnetic, atomic, physico-chemical), returning constants, total count, and available categories.