What Is the Difference Between PUT and PATCH Methods in REST API?

Introduction

When building REST APIs for real-world applications (like e-commerce apps, banking systems, or social platforms), updating data efficiently and safely is critical. Two HTTP methods—PUT and PATCH—are specifically designed for updating resources, but they are often misunderstood or used interchangeably.

This confusion can lead to issues like unnecessary data transfer, accidental data loss, or poor API design.

In this article, we will deeply understand:

What PUT and PATCH methods are
How they work internally
Real-world use cases and scenarios
Key differences in a comparison table
Advantages and disadvantages of each

The goal is to help you design clean, scalable, and production-ready REST APIs.

What Is a REST API?

A REST API (Representational State Transfer) is an architectural style that allows communication between client and server using HTTP protocols.

It follows standard HTTP methods:

GET → Retrieve data
POST → Create data
PUT → Update entire resource
PATCH → Update partial resource
DELETE → Remove data

Each request operates on a resource (like a user, product, or order).

What Is the PUT Method?

PUT is an HTTP method used to completely replace an existing resource with a new version.

Definition:

PUT updates the entire resource by sending a full representation of that resource to the server. If some fields are missing, they may be removed or reset.

How PUT Works Internally

When a PUT request is sent:

The server locates the resource using the given ID or URL
The existing resource is replaced with the new data
Any missing fields may be overwritten or set to default values

Key Characteristics of PUT

Full resource replacement
Idempotent (same request repeated → same result)
Requires complete data
Predictable behavior

Example of PUT Request

Existing user:

{
  "id": 1,
  "name": "Rahul",
  "email": "[email protected]",
  "age": 25
}

PUT request:

PUT /api/users/1

{
  "id": 1,
  "name": "Rahul Sharma",
  "email": "[email protected]",
  "age": 26
}

Here, the entire object is replaced.

Real-Life Scenario (PUT)

Imagine editing your full profile form on a website. You rewrite all fields and submit the entire form again.

What Is the PATCH Method?

PATCH is used to update only specific fields of a resource without affecting the rest of the data.

Definition:

PATCH applies partial modifications to a resource by sending only the fields that need to be changed.

How PATCH Works Internally

The server identifies the resource
Only the provided fields are updated
Remaining fields stay unchanged

PATCH often uses formats like JSON Patch or Merge Patch.

Key Characteristics of PATCH

Partial updates
Efficient (smaller payload)
Not always idempotent (depends on implementation)
More flexible but slightly complex

Example of PATCH Request

PATCH /api/users/1

{
  "email": "[email protected]"
}

Only the email field changes.

Real-Life Scenario (PATCH)

You log in and update only your phone number without touching other profile details.

Difference Between PUT and PATCH

Feature	PUT Method	PATCH Method
Definition	Replaces entire resource	Updates partial resource
Data Sent	Full object	Only changed fields
Idempotency	Always idempotent	May or may not be idempotent
Risk	Can overwrite data	Safer for small updates
Performance	Higher payload	Lower payload
Use Case	Full update	Partial update
Complexity	Simple	Slightly complex

Real-World Use Cases

When to Use PUT (Production Scenarios)

Updating full user profile in admin panel
Replacing entire product details in inventory systems
Synchronizing data from external systems

Example:

An admin updates all product details including name, price, stock, and category.

When to Use PATCH (Production Scenarios)

Updating user email or password
Changing order status (e.g., Pending → Shipped)
Updating a single setting in a large configuration object

Example:

In an e-commerce app, only order status changes—not the entire order.

ASP.NET Core Practical Example

PUT Example

[HttpPut("{id}")]
public IActionResult UpdateUser(int id, User user)
{
    var existingUser = _context.Users.Find(id);
    if (existingUser == null)
        return NotFound();

    existingUser.Name = user.Name;
    existingUser.Email = user.Email;
    existingUser.Age = user.Age;

    _context.SaveChanges();
    return Ok(existingUser);
}

PATCH Example

[HttpPatch("{id}")]
public IActionResult PatchUser(int id, JsonPatchDocument<User> patchDoc)
{
    var user = _context.Users.Find(id);
    if (user == null)
        return NotFound();

    patchDoc.ApplyTo(user);
    _context.SaveChanges();

    return Ok(user);
}

Advantages of PUT

Clear and predictable behavior
Easy to implement and debug
Ensures full consistency of data

Disadvantages of PUT

Requires full payload even for small changes
Higher bandwidth usage
Risk of overwriting fields unintentionally

Advantages of PATCH

Efficient and faster for small updates
Reduces network usage
Ideal for large objects

Disadvantages of PATCH

More complex to implement
Requires proper validation
Can lead to inconsistent state if misused

Before vs After Understanding

Before:

Developers use PUT everywhere
Large unnecessary payloads
Risk of data loss

After:

Smart use of PUT and PATCH
Optimized performance
Cleaner API design

Common Mistakes to Avoid

Using PUT for partial updates
Not validating PATCH data
Ignoring idempotency
Overwriting important fields accidentally

Summary

Understanding the difference between PUT and PATCH is not just a theory—it directly impacts performance, scalability, and reliability of your API.

In simple terms:

Use PUT when you want to replace everything
Use PATCH when you want to change only what is needed

Mastering this concept will help you design better APIs that are efficient, maintainable, and production-ready.