JSON vs JSONB in PostgreSQL: Complete Guide

If you're working with JSON data in PostgreSQL, you've probably wondered: should I use JSON or JSONB? While they might seem similar at first glance, choosing the right one can make a huge difference in your application's performance. The "B" in JSONB stands for "Binary," and that small difference changes everything about how your data is stored and queried.

In this guide, we'll walk through the key differences between JSON and JSONB, explore their performance characteristics, and help you decide which one is right for your use case. Whether you're building a new application or optimizing an existing one, understanding these two data types is essential for working effectively with PostgreSQL.

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What Are JSON and JSONB?

Think of JSON as storing a photo as a text description, while JSONB is like storing it as an actual image file. JSON keeps the exact words you wrote, but JSONB converts it into an optimized format that's easier to work with later.

How They Store Data

Let's see how the same data is handled differently by JSON and JSONB:

{
  "name":    "Alice",
  "age":     30,
  "name":    "Alice Smith",
  "city":    "New York"
}

{
  "name":    "Alice",
  "age":     30,
  "name":    "Alice Smith",
  "city":    "New York"
}

{"age":30,"city":"New York","name":"Alice Smith"}

Key Differences Explained

Complete Comparison Table

Performance Benchmarks

Let's look at some real-world performance differences. These benchmarks are from a PostgreSQL database with 1 million records:

SELECT * FROM users WHERE data->>'email' = '[email protected]';

SELECT * FROM products WHERE data @> '{"category": "electronics"}';

INSERT INTO logs (data) VALUES ('{"timestamp": "2025-01-15", ...}');

SQL Examples

Here are practical examples showing how to work with both types:

-- Using JSON
CREATE TABLE users_json (
    id SERIAL PRIMARY KEY,
    data JSON
);

-- Using JSONB (recommended)
CREATE TABLE users_jsonb (
    id SERIAL PRIMARY KEY,
    data JSONB
);

-- GIN index on entire JSONB column
CREATE INDEX idx_users_data ON users_jsonb USING GIN (data);

-- Index on specific key
CREATE INDEX idx_users_email ON users_jsonb 
USING btree ((data->>'email'));

-- Expression index
CREATE INDEX idx_users_age ON users_jsonb 
USING btree (((data->>'age')::int));

-- Get a specific key (works for both)
SELECT data->>'name' FROM users_jsonb;

-- Containment check (JSONB only)
SELECT * FROM users_jsonb 
WHERE data @> '{"status": "active"}';

-- Key existence (JSONB only)
SELECT * FROM users_jsonb 
WHERE data ? 'phone_number';

-- Multiple keys exist (JSONB only)
SELECT * FROM users_jsonb 
WHERE data ?& ARRAY['email', 'phone'];

-- Update a specific key
UPDATE users_jsonb 
SET data = jsonb_set(data, '{age}', '31')
WHERE id = 1;

-- Add a new key
UPDATE users_jsonb 
SET data = data || '{"verified": true}'::jsonb
WHERE id = 1;

-- Remove a key
UPDATE users_jsonb 
SET data = data - 'temporary_field'
WHERE id = 1;

When to Use Each Type

Converting Between JSON and JSONB

If you started with JSON and want to switch to JSONB (or vice versa), here's how:

-- Convert JSON to JSONB
ALTER TABLE users 
ALTER COLUMN data TYPE JSONB 
USING data::JSONB;

-- Convert JSONB to JSON
ALTER TABLE users 
ALTER COLUMN data TYPE JSON 
USING data::JSON;

-- Add new JSONB column
ALTER TABLE users ADD COLUMN data_jsonb JSONB;

-- Copy and convert data
UPDATE users SET data_jsonb = data::JSONB;

-- Create indexes on new column
CREATE INDEX idx_users_data_jsonb ON users USING GIN (data_jsonb);

-- (After testing) Drop old column
ALTER TABLE users DROP COLUMN data;

-- Rename new column
ALTER TABLE users RENAME COLUMN data_jsonb TO data;

Best Practices

Helpful JSON Tools

Final Thoughts

Choosing between JSON and JSONB in PostgreSQL is usually an easy decision: go with JSONB. The performance benefits, indexing capabilities, and rich set of operators make it the clear winner for almost all use cases. The only time you'd reach for JSON is when you absolutely need to preserve the exact formatting of the input data.

Think of JSONB as the optimized, production-ready version of JSON. It's been processed and organized to make your life easier when you need to query it. Yes, there's a tiny bit of overhead when inserting data, but you'll make that time back (and then some) on your first few queries.