JSON Merge API
Deep-merge JSON objects — the operation every config and settings system needs. The merge endpoint recursively merges two objects (the second overrides the first), or a whole list of objects merged left-to-right, combining nested objects key by key rather than replacing them wholesale, with a choice of array strategy: replace (default), concat, union (concatenate and de-duplicate) or merge_index (merge element by element). A null in the overriding object can either overwrite the existing value or be ignored, so you can patch only the fields you mean to. The defaults endpoint is the inverse and just as useful: it fills in only the keys your data is missing from a defaults object, so your existing values always win — exactly how you layer a user's settings over default configuration. Everything is computed locally and deterministically, with no schema required. Ideal for configuration and feature-flag layering, settings and preference merges, combining API responses or partial updates, environment overrides, and template defaults. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This merges documents; to diff or patch them (RFC 6902) use a JSON-diff API, to flatten them use a flatten API, and to address values use a JSON-Pointer API.
api.oanor.com/jsonmerge-api
