Safe methods vs unsafe methods in Rest API

Introduction

Safe methods help you get data without changing anything. Unsafe methods change or delete data. Knowing the difference keeps your app safe and working well.

When you want to read information from a server without changing it.

When you need to update or delete data on a server.

When building a website that shows data but also lets users add or change it.

When designing APIs that should protect data from accidental changes.

When deciding which HTTP method to use for different actions in your app.

Syntax

Rest API

GET /resource
POST /resource
PUT /resource
DELETE /resource
PATCH /resource

Safe methods like GET do not change data on the server.

Unsafe methods like POST, PUT, DELETE, PATCH can change data.

Examples

This safe method fetches user data without changing it.

Rest API

GET /users/123

This unsafe method creates a new user named Alice.

Rest API

POST /users
{
  "name": "Alice"
}

This unsafe method deletes the user with ID 123.

Rest API

DELETE /users/123

Sample Program

This program shows a safe GET request that reads a post's title without changing anything. Then it shows an unsafe POST request that creates a new post on the server.

Rest API

import requests

# Safe method: GET request to fetch data
response_get = requests.get('https://jsonplaceholder.typicode.com/posts/1')
print('GET status:', response_get.status_code)
print('GET data:', response_get.json()['title'])

# Unsafe method: POST request to create data
response_post = requests.post('https://jsonplaceholder.typicode.com/posts', json={"title": "foo", "body": "bar", "userId": 1})
print('POST status:', response_post.status_code)
print('POST response:', response_post.json())

Important Notes

Safe methods can be repeated many times without changing the server.

Unsafe methods may change or delete data, so use them carefully.

Browsers and servers often treat safe and unsafe methods differently for security.

Summary

Safe methods like GET only read data and do not change anything.

Unsafe methods like POST, PUT, DELETE change data on the server.

Use the right method to keep your app safe and working correctly.

Practice

1. Which HTTP method is considered safe because it only retrieves data without changing anything?

easy

A. DELETE

B. POST

C. PUT

D. GET

Solution

1. Step 1: Understand safe methods

   Safe methods do not change data on the server; they only read or retrieve data.

2. Step 2: Identify the safe method among options

   GET is the method used to request data without modifying it, making it safe.

3. Final Answer:

   GET -> Option D

4. Quick Check:

   Safe method = GET [OK]

Hint: Safe methods only read data, GET is the common safe method [OK]

Common Mistakes:

• Confusing POST as safe
• Thinking PUT is safe
• Assuming DELETE is safe

2. Which of the following is the correct syntax to send data to a server to create a new resource?

easy

A. POST /resource HTTP/1.1

B. GET /resource HTTP/1.1

C. DELETE /resource HTTP/1.1

D. PUT /resource HTTP/1.1

Solution

1. Step 1: Identify method for creating resources

   POST is used to send data to the server to create new resources.

2. Step 2: Check syntax correctness

   POST /resource HTTP/1.1 is the correct syntax to send data for creation.

3. Final Answer:

   POST /resource HTTP/1.1 -> Option A

4. Quick Check:

   Creating resource = POST [OK]

Hint: POST is for sending data to create, syntax includes POST and resource path [OK]

Common Mistakes:

• Using GET to send data
• Confusing DELETE with POST
• Using PUT for creation without context

3. What will be the result of this HTTP request method usage?

PUT /items/123 HTTP/1.1
Content-Type: application/json

{"name": "New Item"}

Choose the correct description.

medium

A. It retrieves the item with ID 123 without changes.

B. It updates or replaces the item with ID 123 with new data.

C. It deletes the item with ID 123 from the server.

D. It creates a new item without specifying an ID.

Solution

1. Step 1: Understand the PUT method purpose

   PUT is used to update or replace an existing resource at a specific URL.

2. Step 2: Analyze the request details

   The request targets /items/123 with JSON data, meaning it updates item 123.

3. Final Answer:

   It updates or replaces the item with ID 123 with new data. -> Option B

4. Quick Check:

   PUT updates resource = C [OK]

Hint: PUT replaces or updates resource at given URL [OK]

Common Mistakes:

• Thinking PUT retrieves data
• Confusing PUT with DELETE
• Assuming PUT creates without ID

4. Identify the error in this HTTP request if the goal is to safely retrieve data:

POST /users HTTP/1.1
Host: example.com

medium

A. The HTTP version is incorrect; it should be HTTP/2.0.

B. The Host header is missing, causing a syntax error.

C. POST is unsafe and changes data; GET should be used to retrieve data.

D. POST cannot be used with /users endpoint.

Solution

1. Step 1: Understand the goal and method used

   The goal is to safely retrieve data, but POST is used which changes data.

2. Step 2: Identify correct method for safe retrieval

   GET is the safe method to retrieve data without side effects.

3. Final Answer:

   POST is unsafe and changes data; GET should be used to retrieve data. -> Option C

4. Quick Check:

   Safe retrieval = GET, not POST [OK]

Hint: Use GET to retrieve data safely, not POST [OK]

Common Mistakes:

• Ignoring method safety
• Thinking Host header is missing
• Confusing HTTP versions

5. You want to design an API endpoint that allows clients to delete a user account safely. Which HTTP method should you use, and why?

hard

A. DELETE, because it explicitly removes the resource on the server.

B. POST, because it can send data and create resources.

C. GET, because it is safe and does not change data.

D. PUT, because it updates existing resources.

Solution

1. Step 1: Identify the action needed

   The goal is to remove (delete) a user account from the server.

2. Step 2: Choose the correct HTTP method for deletion

   DELETE is the method designed to remove resources safely and clearly.

3. Final Answer:

   DELETE, because it explicitly removes the resource on the server. -> Option A

4. Quick Check:

   Deleting resource = DELETE method [OK]

Hint: Use DELETE to remove resources explicitly and safely [OK]

Common Mistakes:

• Using GET for deletion
• Confusing POST with DELETE
• Using PUT instead of DELETE