> ## Documentation Index
> Fetch the complete documentation index at: https://docs.qu.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Utf8ErrorReason

```ts theme={null}
type Utf8ErrorReason: 
  | "UNEXPECTED_CONTINUE"
  | "BAD_PREFIX"
  | "OVERRUN"
  | "MISSING_CONTINUE"
  | "OUT_OF_RANGE"
  | "UTF16_SURROGATE"
  | "OVERLONG";
```

When using the UTF-8 error API the following errors can be intercepted and processed as the `reason` passed to the
[**Utf8ErrorFunc**](/sdk/content/type-aliases/Utf8ErrorFunc).

**`"UNEXPECTED_CONTINUE"`** - a continuation byte was present where there was nothing to continue.

**`"BAD_PREFIX"`** - an invalid (non-continuation) byte to start a UTF-8 codepoint was found.

**`"OVERRUN"`** - the string is too short to process the expected codepoint length.

**`"MISSING_CONTINUE"`** - a missing continuation byte was expected but not found. The `offset` indicates the index
the continuation byte was expected at.

**`"OUT_OF_RANGE"`** - the computed code point is outside the range for UTF-8. The `badCodepoint` indicates the
computed codepoint, which was outside the valid UTF-8 range.

**`"UTF16_SURROGATE"`** - the UTF-8 strings contained a UTF-16 surrogate pair. The `badCodepoint` is the computed
codepoint, which was inside the UTF-16 surrogate range.

**`"OVERLONG"`** - the string is an overlong representation. The `badCodepoint` indicates the computed codepoint,
which has already been bounds checked.

## Source

[encoding/utf8.ts:45](https://github.com/dominant-strategies/quais.js/blob/c1c12d43f9d34c6baad2b0542bd6d0acd6fefcbf/src/encoding/utf8.ts#L45)