Plural vs singular resource names in Rest API - Visual Side-by-Side Comparison

Concept Flow - Plural vs singular resource names

Client sends request

↓

Check resource name

↓

Plural

↓

Handle as collection

↓

Return response

The API checks if the resource name is plural or singular to decide if it handles a collection or a single item.

Execution Sample

Rest API

GET /users
GET /user/123
POST /users
DELETE /user/123

Shows requests using plural for collections and singular for single items.

Execution Table

Step	Request	Resource Name	Type	Action	Response
1	GET /users	users	Plural	Return list of users	200 OK with user list
2	GET /user/123	user	Singular	Return user with ID 123	200 OK with user data
3	POST /users	users	Plural	Create new user in collection	201 Created
4	DELETE /user/123	user	Singular	Delete user with ID 123	204 No Content
5	GET /user	user	Singular	Missing ID, error	400 Bad Request

💡 Requests stop after response is sent.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5
Resource Name		users	user	users	user	user
Type		Plural	Singular	Plural	Singular	Singular
Action		Return list	Return single	Create new	Delete single	Error - missing ID
Response		200 OK list	200 OK single	201 Created	204 No Content	400 Bad Request

Key Moments - 3 Insights

Why do we use plural names like /users for collections?

Plural names clearly indicate the resource is a collection, so the API returns multiple items, as shown in execution_table rows 1 and 3.

What happens if we use singular without an ID, like GET /user?

The API expects an ID for singular resources. Without it, it returns an error, as seen in execution_table row 5.

Can singular resource names be used for creating new items?

No, creation is done on the collection (plural) endpoint, like POST /users in row 3.

Visual Quiz - 3 Questions

Look at the execution_table, what type is the resource name 'users' in step 1?

A Singular

B Plural

C Unknown

D Both

💡 Hint

Check the 'Type' column in execution_table row 1.

At which step does the API return a 400 Bad Request error?

A Step 2

B Step 3

C Step 5

D Step 4

💡 Hint

Look at the 'Response' column for the error status in execution_table.

If we change POST /users to POST /user, what would likely happen?

A Return an error because singular is for single items

B Return list of users

C Create a new user successfully

D Delete a user

💡 Hint

Refer to key_moments about creation using plural resource names.

Concept Snapshot

Use plural resource names (e.g., /users) for collections.
Use singular resource names (e.g., /user/123) for single items.
POST and GET on plural handle collections.
GET, DELETE on singular handle single items.
Missing ID on singular causes errors.

Full Transcript

This visual execution shows how REST APIs use plural resource names for collections and singular names for single items. The API checks the resource name in the request. If plural, it treats it as a collection and returns or modifies multiple items. If singular with an ID, it handles a single item. Missing IDs on singular resources cause errors. For example, GET /users returns a list, while GET /user/123 returns one user. POST is done on plural to create new items. This helps keep API design clear and consistent.

Practice

1. Which naming style is recommended for an API endpoint that returns a list of users?
/user or /users?

easy

A. /users because it is singular and more precise.

B. /user because it is shorter and simpler.

C. /user because it is singular and more precise.

D. /users because it represents multiple users.

Solution

1. Step 1: Understand resource naming for collections

   API endpoints returning multiple items should use plural names to clearly indicate a list.

2. Step 2: Apply naming to the example

   Since the endpoint returns multiple users, /users is the correct plural form.

3. Final Answer:

   /users because it represents multiple users. -> Option D

4. Quick Check:

   Plural for lists = /users [OK]

Hint: Use plural names for endpoints returning lists [OK]

Common Mistakes:

• Using singular for list endpoints
• Confusing singular and plural forms
• Choosing shorter names over clarity

2. Which of the following is the correct endpoint to access a single product by its ID?

easy

A. /products/123

B. /product/123

C. /products

D. /product

Solution

1. Step 1: Identify singular vs plural for single item access

   When accessing a single item by ID, use the plural form of the resource name followed by the ID.

2. Step 2: Match the correct endpoint format

   The endpoint /products/123 uses plural products and includes the ID, which is the common RESTful convention.

3. Final Answer:

   /products/123 -> Option A

4. Quick Check:

   Single item access = plural + ID [OK]

Hint: Use plural resource name when accessing one item by ID [OK]

Common Mistakes:

• Using singular resource name for single item
• Omitting the ID when accessing a single item
• Mixing singular/plural inconsistently

3. Given the following API endpoints, which one correctly retrieves a list of orders?

GET /order
GET /orders
GET /order/456
GET /orders/456

medium

A. GET /order

B. GET /orders/456

C. GET /orders

D. GET /order/456

Solution

1. Step 1: Identify endpoints returning lists

   Endpoints returning lists should use plural resource names without an ID.

2. Step 2: Analyze each option

   GET /orders uses plural and no ID, so it returns the list of orders. Others either use singular or include an ID, indicating single item access.

3. Final Answer:

   GET /orders -> Option C

4. Quick Check:

   List retrieval = plural resource without ID [OK]

Hint: Plural + no ID means list retrieval [OK]

Common Mistakes:

• Choosing singular endpoint for list
• Confusing ID presence with list retrieval
• Ignoring plural vs singular rules

4. You have an API endpoint defined as GET /users/ to get a list of users and GET /user/{id} to get a single user. A developer mistakenly uses GET /user/ to get all users. What is the likely problem?

medium

A. The endpoint /user/ is incorrect for list retrieval and may cause a 404 error.

B. The endpoint /user/ will return a list of users anyway.

C. The endpoint /user/ will return a single user without ID.

D. The endpoint /user/ will automatically redirect to /users/.

Solution

1. Step 1: Understand endpoint naming conventions

   List retrieval requires plural resource name, so /users/ is correct for all users.

2. Step 2: Analyze the incorrect usage

   /user/ is singular and without an ID, so it likely does not exist or returns an error like 404.

3. Final Answer:

   The endpoint /user/ is incorrect for list retrieval and may cause a 404 error. -> Option A

4. Quick Check:

   Singular without ID ≠ list endpoint [OK]

Hint: Singular without ID usually causes errors for list requests [OK]

Common Mistakes:

• Using singular endpoint for list retrieval
• Assuming singular endpoint returns list
• Expecting automatic redirects between endpoints

5. You are designing an API for a library system. Which of the following endpoint designs correctly follows the plural vs singular resource naming best practices for retrieving a single book and all books?

hard

A. GET /book for all books and GET /books/{id} for a single book

B. GET /books for all books and GET /book/{id} for a single book

C. GET /books/{id} for all books and GET /book for a single book

D. GET /book/{id} for all books and GET /books for a single book

Solution

1. Step 1: Recall naming rules for collections and single items

   Use plural resource names for collections (all books) and singular for single items by ID.

2. Step 2: Match options to rules

   GET /books correctly retrieves all books (plural). GET /book/{id} correctly retrieves a single book (singular with ID).

3. Final Answer:

   GET /books for all books and GET /book/{id} for a single book -> Option B

4. Quick Check:

   Plural for list, singular + ID for single [OK]

Hint: Plural for lists, singular + ID for single items [OK]

Common Mistakes:

• Swapping singular and plural for list vs single
• Using singular without ID for list
• Using plural with ID for single item