De-Obfuscating Phone Numbers: The Custom Font Trick
To discourage data scrapers, Justdial pioneered replacing phone number digits with custom CSS background icon classes (e.g. <span class="icon-dc"></span>) or custom web fonts where character glyphs are deliberately scrambled.
The Decoding Algorithm
The Digital Mart JD Extractor Chrome Extension reverses this obfuscation dynamically in the user's authenticated browser session. By parsing the computed font-family metrics and CSS sprite coordinates, the extension maps glyph classes back to their true decimal values (0-9) with 100% precision.
Ethical Crawling Principles
Respect target server resources by throttling request rates, avoiding denial-of-service patterns, and restricting scraping exclusively to publicly listed business directories meant for public vendor discovery.
