HTTP Status Codes Overview 📊

Status codes are three-digit numbers that tell the client what happened with their request. Understanding them is essential for API development.

Status Code Categories

Status codes are grouped into five categories:

• **1xx (Informational)**: Request received, continuing process

• **2xx (Success)**: Request succeeded

• **3xx (Redirection)**: Further action needed

• **4xx (Client Error)**: Request has an error

• **5xx (Server Error)**: Server failed to fulfill request

Common Status Codes

Using Status Codes in FastAPI

from fastapi import status

@app.get("/items/{item_id}", status_code=status.HTTP_200_OK)
async def get_item(item_id: int):
    return {"id": item_id}

@app.post("/items", status_code=status.HTTP_201_CREATED)
async def create_item(item: dict):
    return item

@app.delete("/items/{item_id}", status_code=status.HTTP_204_NO_CONTENT)
async def delete_item(item_id: int):
    return None

Real-World Example

@app.get("/users/{user_id}")
async def get_user(user_id: int):
    user = db.get_user(user_id)
    if not user:
        # 404 if not found
        raise HTTPException(status_code=404, detail="User not found")
    # 200 if found
    return user

🔑 Key Takeaways

• ✅ Status codes indicate request outcome

• ✅ 2xx = success, 4xx = client error, 5xx = server error

• ✅ Use specific codes for clarity

• ✅ Codes guide client behavior