JSON Flattener / Unflattener

Flatten deeply nested JSON to a flat object with dotted keys (user.address.city) — useful for tools that expect flat KV (analytics, logs, env vars). Or unflatten dotted-key data back into nested form.

How to use the JSON Flattener / Unflattener

Flatten: paste nested JSON, get back a flat object. Unflatten: paste a flat object with dotted keys, get the nested structure. Round-trip is exact for objects without numeric-string-only keys.