# No byte-order mark (`no-bom`)

`no-bom` warns against having the byte-order mark (BOM) character
at the beginning of a text file.

## Why is this important?

Having the BOM character at the beginning of a file over the internet
(especially HTML) can have some bad side effects on some browsers.
The BOM character can be used to indicate the charset of the content
is `UTF-8` but this doesn't mean it will be considered. For example,
Internet Explorer 10 and 11 give a higher precedence to the HTTP header
while previous versions gave the precedence to BOM for the encoding.

You can learn about other problems in [this section][bom problems].

## What does the hint check?

This hint checks that all text-based media type files are served
without the BOM character at the beginning.

### Examples that **trigger** the hint

A text file (such as HTML) that starts with the BOM character `U+FEFF`
will fail.

### Examples that **pass** the hint

A text file (such as HTML) that doesn't start with the BOM character
`U+FEFF` will pass.

## How to use this hint?

This package is installed automatically by webhint:

```bash
npm install hint --save-dev
```

To use it, activate it via the [`.hintrc`][hintrc] configuration file:

```json
{
    "connector": {...},
    "formatters": [...],
    "hints": {
        "no-bom": "error",
        ...
    },
    "parsers": [...],
    ...
}
```

**Note**: The recommended way of running webhint is as a `devDependency` of
your project.

## Further Reading

* [Byte order mark (Wikipedia)][bom]
* [The byte-order mark (BOM) in HTML][bom in html]

<!-- Link labels: -->

[bom]: https://en.wikipedia.org/wiki/Byte_order_mark
[bom in html]: https://www.w3.org/International/questions/qa-byte-order-mark.en
[bom problems]: https://www.w3.org/International/questions/qa-byte-order-mark.en#problems
[hintrc]: https://webhint.io/docs/user-guide/configuring-webhint/summary/