Within Reach: A local-first marketplace, worldwide by choice

Within Reach proposes a model for online marketplaces in which the buyer and the seller each set a geographic reach — local, state, country, or worldwide — and a listing is visible only where the two reaches overlap: the seller must sit within the buyer's reach, and the buyer within the seller's. This two-sided rule sorts participants by where they are and how far they will trade, never by size, so a local seller cannot be buried by a global one, and trade that cannot ship — produce, pickup-only, hand-delivered goods — gets a home that global platforms cannot structurally host. The paper sets out the principle, who it serves, a reference of the single matching rule, and how the idea is kept open. It is published as prior art to keep the idea freely available, and is accompanied by an open-source reference implementation.