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What is PUT used for?

Networking & InternetMiddle~1 min read
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PUT is an HTTP method used to fully update (replace) a resource on the server.

In simple terms: PUT is needed to replace existing data with new data entirely.

The main purpose of PUT

PUT is used when you need to:

  • update an existing resource
  • replace its current state with a new one
  • save data at a specific address (URL)

The typical meaning of PUT:

"Here is new data, make the resource look exactly like this"

How PUT works

  1. The client sends an HTTP request with the PUT method
  2. The request body carries all of the resource's data
  3. The server:
  • finds the resource by its URL
  • fully replaces its content
  1. The server returns an HTTP response

If some field is missing from the PUT request, it may be removed or reset.

Where data is sent with PUT

Data is sent:

  • in the request body
  • usually as JSON or XML

An example of what the request means:

json
{ "id": 123, "name": "Alice", "email": "alice@example.com" }

A key property of PUT

Idempotency

PUT is an idempotent method:

  • send PUT once, and the resource is updated
  • send the same PUT 10 times, and the result is the same

This is a key difference from POST.

PUT vs POST (short and clear)

  • POST
    • create a resource
    • the action can repeat with a different result
  • PUT
    • update (or replace) a resource
    • a repeated request gives the same result

A way to remember it:

  • POST - "create"
  • PUT - "replace"

Real-life example

PUT is like:

  • replacing a form entirely with a new version
  • rewriting a document completely
  • saving a file over the old one

You are not fixing individual lines, you are changing everything at once.

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