> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # Dart Runes In Dart, **Runes** are an iterable sequence of 32-bit Unicode code points that represent a string. Because Dart strings are inherently sequences of UTF-16 code units, characters outside the Basic Multilingual Plane (BMP)—such as emojis or complex symbols—are represented in memory by surrogate pairs (two 16-bit units). The `Runes` class abstracts this UTF-16 encoding complexity, allowing developers to interact directly with the underlying 32-bit Unicode code points. ## Syntax and String Literals Within a Dart string literal, Unicode code points are expressed using the `\u` escape sequence followed by a hexadecimal value. * **4-digit hexadecimal:** Used for characters within the BMP. * **Curly braces `{}`:** Required for hexadecimal values containing more or fewer than 4 digits (characters outside the BMP). ```dart theme={"dark"} String heart = '\u2665'; // 4-digit hex (BMP) String rocket = '\u{1F680}'; // 5-digit hex (Non-BMP, requires braces) ``` ## Technical Mechanics: `codeUnits` vs `runes` The distinction between a standard Dart `String` and `Runes` becomes apparent when inspecting string length and character data. A string's `.length` property returns the number of UTF-16 code units, not the number of visible characters. The `.runes` property returns an `Iterable` representing the actual Unicode code points. ```dart theme={"dark"} String emoji = '🚀'; // UTF-16 Representation print(emoji.length); // Output: 2 (Surrogate pair) print(emoji.codeUnits); // Output: [55357, 56960] // 32-bit Unicode Representation print(emoji.runes.length); // Output: 1 (Single code point) print(emoji.runes); // Output: (128640) ``` ## Instantiation and Conversion You can instantiate a `Runes` object directly from a string, and you can reconstruct a `String` from an iterable of runes using the `String.fromCharCodes()` constructor. ```dart theme={"dark"} // Extracting runes from a string Runes runeSequence = Runes('\u2665 \u{1f605}'); // Iterating over the 32-bit integers for (int codePoint in runeSequence) { print(codePoint); // Output: 9829, 32, 128517 } // Reconstructing a String from Runes String reconstructed = String.fromCharCodes(runeSequence); print(reconstructed); // Output: ♥ 😅 ``` ## Character API Alternative While `Runes` provide raw integer code points, Dart also offers the `characters` package (often exposed via the `String.characters` extension). While `Runes` handle 32-bit code points, `characters` handle *grapheme clusters* (user-perceived characters), which is necessary when a single visual character is composed of multiple Unicode code points (e.g., an emoji with a skin tone modifier).

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