Highlightr
iOS & macOS syntax highlighter built with Swift, using highlight.js to support 185 languages and 89 styles.
What is Highlightr?
Highlightr is an iOS and macOS syntax highlighter built with Swift that uses highlight.js to convert plain code strings into formatted NSAttributedString objects. It supports 185 programming languages and 89 visual styles, enabling developers to add syntax highlighting to text editors, code viewers, or any app displaying code. The project solves the need for a ready-to-use, multi-language syntax highlighter within Apple's ecosystem without requiring native parsing implementations.
iOS and macOS developers building applications that display or edit code, such as code editors, documentation tools, educational apps, or developer utilities. It's particularly useful for those who need broad language support and customizable themes without implementing highlighting from scratch.
Developers choose Highlightr because it leverages the widely-used highlight.js library, providing extensive language support and theme variety out of the box. Its integration with Swift and Apple's JavaScriptCore ensures decent performance for real-time editing, while its simple API makes it easy to add syntax highlighting to existing projects.
Overview
iOS & OSX Syntax Highlighter.
Use Cases
Best For
- Adding syntax highlighting to iOS or macOS code editor apps
- Displaying formatted code snippets in documentation or tutorial apps
- Building educational coding apps that need multi-language support
- Enhancing developer tools with real-time code highlighting
- Creating custom text editors with live syntax feedback
- Embedding code examples in Swift-based applications with styled output
Not Ideal For
- Projects requiring long-term support and active maintenance due to its deprecated status
- Real-time code editors with strict performance budgets for large files or low-latency requirements
- Teams needing a pure Swift implementation to avoid JavaScriptCore overhead or for App Store optimization
- Cross-platform applications targeting non-Apple ecosystems like Android or web
Pros & Cons
Pros
Supports 185 programming languages by leveraging highlight.js, eliminating the need to implement custom parsers for each language, as stated in the README.
Comes with 89 pre-built visual styles, allowing developers to easily customize syntax highlighting appearance without creating themes from scratch.
Provides CodeAttributedString, a subclass of NSTextStorage, enabling live syntax highlighting in text editors, which is ideal for interactive coding apps.
Can detect the programming language from code strings if not specified, simplifying integration for dynamic or user-submitted code snippets.
Offers a straightforward API to convert plain strings to NSAttributedString objects with minimal setup, using Swift Package Manager for installation.
Cons
As of 2026, Highlightr is no longer actively maintained, with the author recommending HighlighterSwift instead, posing risks for bug fixes and compatibility updates.
Relies on JavaScriptCore to run highlight.js, which is slower than native Swift parsers and adds runtime dependency, as admitted in the README's performance section.
The bundled highlight.js library is static and not updated, potentially missing new languages, features, or security patches from the upstream project.
Lacks active community support, and documentation is hosted on Cocoadocs which may not be current, making troubleshooting difficult for new issues.
Frequently Asked Questions
Related Projects
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ZSSRichTextEditorA beautiful rich text WYSIWYG editor for iOS with a syntax highlighted source view
BonMotBeautiful, easy attributed strings in Swift
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