JSON vs JSONB: Understanding the Difference

PostgreSQL provides two JSON data types: json and jsonb. While both store JSON data, they differ significantly in storage, performance, and functionality.

JSON Type

The json type stores an exact copy of the input text:

sql
SELECT '{"bar": "baz", "balance": 7.77, "active":false}'::json;
-- Preserves whitespace and key order exactly

Characteristics:

• Stores exact input text
• Preserves whitespace and key order
• Preserves duplicate keys
• Must reparse on each operation
• Cannot be indexed (except expression indexes)

JSONB Type

The jsonb type stores data in a decomposed binary format:

sql
SELECT '{"bar": "baz", "balance": 7.77, "active":false}'::jsonb;
-- Output: {"bar": "baz", "active": false, "balance": 7.77}
-- Keys reordered, whitespace normalized

Characteristics:

• Binary storage format
• Removes whitespace, reorders keys
• Removes duplicate keys (last value wins)
• Faster to process (pre-parsed)
• Supports GIN indexing
• Supports additional operators

When to Use Each

Best Practice: Use jsonb in 95% of cases. Only use json when you need exact text preservation.

-- JSON preserves exact input
SELECT '{"a":1,"a":2}'::json;  -- {"a":1,"a":2} (both keys kept)

-- JSONB deduplicates keys
SELECT '{"a":1,"a":2}'::jsonb;  -- {"a": 2} (last value wins)

-- Performance difference
CREATE TABLE json_test (data json);
CREATE TABLE jsonb_test (data jsonb);

-- JSONB can be indexed
CREATE INDEX ON jsonb_test USING GIN (data);