How to Customize 404 Not Found Error Page in FastAPI?

Customizing 404 Not Found Error Page in FastAPI

In web development, it is common practice to create custom error pages for different HTTP status codes to enhance user experience. In this article, we will explore how to create a custom 404 Not Found page using FastAPI, a popular Python web framework.

FastAPI offers several methods to handle custom exceptions and errors. Let's dive into the various solutions available.

Exception Handler

To define a custom exception handler, use the @app.exception_handler(exception_to_handle) decorator. For handling 404 errors, the following code can be used:

<code class="python">@app.exception_handler(404)
async def not_found_error(request: Request, exc: HTTPException):
    return RedirectResponse('https://fastapi.tiangolo.com')</code>

Custom Middleware

FastAPI allows for the use of custom middleware to intercept requests and responses. To create a middleware for 404 error handling:

<code class="python">@app.middleware("http")
async def redirect_on_not_found(request: Request, call_next):
    response = await call_next(request)
    if response.status_code == 404:
        return RedirectResponse("https://fastapi.tiangolo.com")
    else:
        return response</code>

Exception Handlers Parameter

Alternatively, exception handers can be specified as a parameter of the FastAPI class:

<code class="python">async def not_found_error(request: Request, exc: HTTPException):
    return RedirectResponse('https://fastapi.tiangolo.com')

exception_handlers = {404: not_found_error}
app = FastAPI(exception_handlers=exception_handlers)</code>

Customizing the Error Response

In the code snippets provided above, we return a RedirectResponse to redirect the user to a different page. However, you can also return a custom HTMLResponse or Jinja2TemplateResponse to create a custom error page with the appropriate content.

We hope this guide helps you create custom 404 error pages in FastAPI and enhance the user experience on your web application.

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