Languages

The default registry contains 27 languages. Pass the identifier in the Identifier column to Highlighter::highlight().

Identifiers are case-insensitive after trimming, but there are no short aliases. Use javascript, not js; typescript, not ts; bash, not sh; yaml, not yml; and csharp, not cs.

Read Embedded languages for HTML, SVG, Markdown, and Twig delegation.

Default registry

Language	Identifier	Category	Typical extension	Parsing focus	Example
Bash	`bash`	Shell	`.sh`	Shell keywords, built-ins, variables, strings, and here-docs	Source
C#	`csharp`	Programming	`.cs`	Two-pass definitions, calls, and type references	Source
CSS	`css`	Stylesheet	`.css`	Selectors, declarations, values, comments, and at-rules	Source
Diff	`diff`	Change	`.diff`	File headers, hunks, added lines, and removed lines	Source
Dockerfile	`dockerfile`	Build	`Dockerfile`	Instructions, modifiers, variables, strings, and comments	Source
dotenv	`dotenv`	Configuration	`.env`	Assignments, `export`, references, values, and comments	Source
Go	`go`	Programming	`.go`	Two-pass functions, methods, receivers, and type references	Source
HTML	`html`	Markup	`.html`	Tags, attributes, text, and embedded CSS or JavaScript	Source
HTTP	`http`	Protocol	`.http`	Request or response lines, headers, and body text	Source
INI	`ini`	Configuration	`.ini`	Sections, assignments, typed values, references, and comments	Source
Java	`java`	Programming	`.java`	Two-pass definitions, calls, types, and brace context	Source
JavaScript	`javascript`	Programming	`.js`	Declarations, calls, literals, templates, and regular expressions	Source
JSON	`json`	Data	`.json`	Object keys, strings, numbers, booleans, and null	Source
Makefile	`makefile`	Build	`.mk`	Targets, dependencies, recipes, variables, and directives	Source
Markdown	`markdown`	Markup	`.md`	Blocks, inline markup, and registered fenced languages	Source
PHP	`php`	Programming	`.php`	Two-pass semantic definitions, calls, types, and variables	Source
Python	`python`	Programming	`.py`	Two-pass function and class definitions, calls, and references	Source
Ruby	`ruby`	Programming	`.rb`	Two-pass definitions, calls, constants, and variables	Source
Rust	`rust`	Programming	`.rs`	Two-pass definitions, calls, types, lifetimes, and macros	Source
SCSS	`scss`	Stylesheet	`.scss`	CSS plus variables, nesting, mixins, and interpolation	Source
SQL	`sql`	Data	`.sql`	Keywords, functions, identifiers, literals, and comments	Source
SVG	`svg`	Markup	`.svg`	XML-style markup plus embedded CSS or JavaScript	Source
Swift	`swift`	Programming	`.swift`	Two-pass definitions, calls, types, attributes, and variables	Source
Twig	`twig`	Templating	`.twig`	Twig expressions and tags with embedded HTML by default	Source
TypeScript	`typescript`	Programming	`.ts`	JavaScript plus types, interfaces, enums, and decorators	Source
XML	`xml`	Markup	`.xml`	Tags, attributes, processing instructions, and CDATA	Source
YAML	`yaml`	Data	`.yaml`	Mappings, sequences, anchors, aliases, values, and comments	Source

The source files above are the canonical compact documentation examples. See Examples for generated previews.

PHP snippets without an opening tag

Selecting php parses PHP from the first byte, including when the opening tag is omitted:

<?php

$html = $highlighter->highlight(
    '$total = array_sum($prices);',
    'php',
);

Any synthetic context required by PHP's native tokenizer is absent from the returned stream, so text, byte offsets, lines, and columns describe the exact source supplied by the caller.

The historical php-snippet identifier remains a compatibility alias for php; it is not a 28th registered language. New code should use php.

Register a custom language

Custom parsers implement LanguageInterface and return a ParsedStream:

<?php

use Alto\Code\Highlight\Language\LanguageInterface;
use Alto\Code\Highlight\Parser\ParsedStream;
use Alto\Code\Highlight\Parser\ParsedToken;
use Alto\Code\Highlight\Scope;

final class MyLanguage implements LanguageInterface
{
    public function getIdentifier(): string
    {
        return 'my-language';
    }

    public function parse(string $code): ParsedStream
    {
        return new ParsedStream([
            new ParsedToken($code, Scope::MarkupText),
        ]);
    }
}

$highlighter->registerLanguage(new MyLanguage());

Registering an existing identifier replaces that parser on the highlighter instance. Theme authors style the generic semantic scopes emitted by parsers; see Creating a theme.

Extension contract

Custom parsers implement LanguageInterface and return a ParsedStream made of ParsedToken values. StreamBuilder, TokenType, and Scope are supported building blocks. Languages::getDefaultLanguages() returns the built-in registry.

Embedded parsers use EmbeddedLanguageCapable, EmbeddedLanguageContext, and the public types under Alto\Code\Highlight\Embedded. Their documented constructors and methods follow the same compatibility promise described in Compatibility.