When to Use POST, PUT, or PATCH? Clear Differences Explained

Introduction

“Hello, can you fix computers here?” ABC: “No.” “Which method should I use to change a username?” A: “Use POST.” B: “Use PUT.” C: “Use PATCH.” “Great, let’s go with A.” “Okay.”

Are you the kind of programmer who gets taken away for not knowing the difference?

I recently realized I could not correctly explain POST, PUT, and PATCH. After using them for years, I finally investigated which method fits a given API scenario and clarified their distinctions.

Why POST/PUT/PATCH Are Often Confused

PUT and PATCH are both used for updates.

The exact usage may vary by framework or API design (some APIs allow partial updates with PUT).

These methods are introduced early in learning, making them seem interchangeable.

Difference Between POST and PUT

According to the Zalando RESTful API guide:

POST on a collection means “add an object to the resource collection identified by the URL.” PUT means “replace the existing resource identified by the URL with the given object.”

In practice, POST creates a new resource, while PUT updates an existing one.

# POST</code>
<code>/v1/user

Using PUT:

# PUT</code>
<code>/v1/users/12345

So, adding a user uses POST, while updating the user with ID 12345 (e.g., changing the name) uses PUT.

Difference Between PUT and PATCH

PATCH means “apply partial modifications to the resource identified by the URL.”

PATCH can modify parts of a resource and, if the resource does not exist, may create it.

# PUT</code>
<code>curl -XPUT /v1/users/12345 -d '{ "age": 31 }'

This updates the age of user 12345 to 31.

# PATCH</code>
<code>curl -XPATCH /v1/users/12345 -d '{ "name": "mina", "age": 31, "email": "[email protected]" }'

With PATCH, only the specified fields (e.g., age) are changed; other fields remain untouched. If the user does not exist, a new one can be created (similar to POST).

Conclusion

Many engineers, even experienced ones, struggle to correctly explain the distinction between POST and PUT. Mastering these fundamentals is essential for becoming a strong backend developer.