Instantly test and visualize OpenType font features like ligatures, stylistic sets, and small caps. A free, browser-based typography tool for web designers.
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OpenType Feature Tester & CSS Property Previewer
Overview
This single-file application is a professional typography utility designed for web designers and front-end developers. It allows users to input text, upload font files, and interactively toggle OpenType features using standard CSS font-feature-settings tags. The tool provides a clean, responsive interface to view the immediate visual impact of typography changes.
Core Features
- Live Typography Preview: A large, editable text area that renders custom fonts in real-time.
- Font File Upload: Support for drag-and-drop or file-picker upload of
.ttf,.otf,.woff, and.woff2fonts. - Dynamic Tag Toggling: A control panel with checkboxes for common OpenType tags (e.g.,
liga,dlig,hlig,ss01throughss20,onum,lnum). - CSS Code Export: A dedicated read-only field that generates the exact CSS string based on the current selections for easy copying.
- Preset Testing Sentences: One-click buttons to load pangrams and specific test strings designed to trigger ligatures and stylistic sets.
UI/UX Specification
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Layout:
- Header: Descriptive title and a minimalist instruction modal trigger.
- Control Sidebar (Left/Top): A clean panel featuring a font upload zone, a list of checkboxes for specific OpenType features, and range sliders for font-size and letter-spacing.
- Preview Area (Center/Main): A large, whitespace-heavy central canvas where the user's text is rendered using the custom font and applied features.
- Code Output Section (Bottom): A fixed-width code block displaying the current
font-feature-settingsCSS syntax.
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Design Aesthetic:
- Color Palette: High-contrast light mode. Off-white background (#F9FAFB), crisp dark text for readability (#111827), and a primary accent color of soft indigo (#4F46E5) for active states and toggles.
- Typography: System-safe sans-serif fonts (Inter, system-ui) for the UI to ensure the focus remains on the uploaded test font.
- Animations: Smooth CSS transitions on hover (scale/shadow) and opacity fades when toggling features. No jarring movements.
Technical Implementation Directives
- Single-File Requirement: All HTML, CSS (Tailwind via CDN), and Vanilla JavaScript must be contained in a single file.
- No Persistence: Absolutely no
localStorage,sessionStorage, or cookies. State is held in volatile memory variables. - Iframe Compatibility: The app must be fully functional within a
nullorigin iframe. Use explicit pathing for any external assets (icons/fonts). - Accessibility: Use semantic HTML5 tags (
<main>,<section>,<header>). Ensure high-contrast ratios for all buttons and text elements. - Responsive Design: Control panel collapses into a mobile-friendly drawer or stacked list on screens smaller than 768px.
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Frequently Asked Questions
Everything you need to know about using this application.
What are OpenType features and how does this tool test them?
OpenType features are advanced typographic capabilities built into modern font files that allow for sophisticated text rendering. These include elements like ligatures (connecting letters), stylistic sets (alternative character shapes), and tabular figures (aligned numbers). This tool allows you to manipulate CSS 'font-feature-settings' dynamically in your browser. By selecting a font and toggling specific tags like 'liga', 'ss01', or 'dlig', you can immediately see how these features affect your text layout without needing to write custom code or use complex design software.
Can I use my own custom fonts with this OpenType tester?
Yes, you can easily load your own font files into the browser environment. The application supports common web font formats such as WOFF, WOFF2, and TTF, ensuring that you can preview your specific typography projects accurately. Because this tool runs entirely in your browser memory and does not save files to a server, it is a private and secure way to test proprietary fonts. Simply upload your file via the interface to begin manipulating OpenType tags and testing character variations.
Why is 'font-feature-settings' important for web typography?
Using the 'font-feature-settings' CSS property gives designers granular control over how text appears on the web. It enables the use of professional typographic standards that would otherwise default to standard, less polished forms, significantly improving readability and visual hierarchy. By leveraging this tool, developers can determine which specific OpenType features are supported by a chosen typeface. This prevents the display of broken characters and ensures that high-quality font features are successfully implemented in final production environments.
Is this tool free and does it store my data?
This OpenType feature tester is a completely free, browser-based utility designed for designers, developers, and typography enthusiasts. We believe in providing accessible tools that work instantly without hidden costs or subscriptions. To ensure your privacy and security, this application does not use cookies, local storage, or server-side databases. All data processing occurs locally within your browser's memory, meaning your uploaded fonts and text inputs are cleared the moment you close the browser tab.
