When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

These exceptions can be imported directly from `fastapi`:

```python
from fastapi import HTTPException, WebSocketException
```

::: fastapi.HTTPException

// Copyright 2025 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

TEXT errors(SB),$0
	VSHUF4IV	$16, V1, V2	// ERROR "operand out of range 0 to 15"
	XVSHUF4IV	$16, X1, X2	// ERROR "operand out of range 0 to 15"
	ADDV16		$1, R4, R5	// ERROR "the constant must be a multiple of 65536."

The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException` { #use-httpexception }

To return HTTP responses with errors to the client you use `HTTPException`.

### Import `HTTPException` { #import-httpexception }

{* ../../docs_src/handling_errors/tutorial001.py hl[1] *}

| `minio_notify_events_errors_total`             | Events that were failed to be sent to the targets (deprecated, please use `minio_notify_target_failed_events` instead)                      |

            }
        };
    }

    // #for_now jflute to suppress CVE-2014-0050 even if commons-fileupload is older than safety version (2024/09/08)
    // but if you use safety version, this extension is basically unneeded (or you can use it as double check)
    protected void checkBoundarySize(final String contentType, final byte[] boundary) {
        final int boundarySize = boundary.length;

/*
 * Copyright (C) 2016 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,

/// tip

The next sections are **not necessarily "advanced"**.

And it's possible that for your use case, the solution is in one of them.

///

## Read the Tutorial first { #read-the-tutorial-first }

#!/usr/bin/env bash
# Copyright 2023 The Go Authors. All rights reserved.
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file.

case "$GOWASIRUNTIME" in
	"wasmedge")
		exec wasmedge --dir=/ --env PWD="$PWD" --env PATH="$PATH" ${GOWASIRUNTIMEARGS:-} "$1" "${@:2}"
		;;
	"wasmer")
		exec wasmer run --dir=/ --env PWD="$PWD" --env PATH="$PATH" ${GOWASIRUNTIMEARGS:-} "$1" -- "${@:2}"
		;;
	"wazero")

not use beta APIs, unless you [repackage] them. **If your
code is a library, we strongly recommend using the [Guava Beta Checker] to
ensure that you do not use any `@Beta` APIs!**

[Guava Beta Checker]: https://github.com/google/guava-beta-checker

<!-- References -->