YOU might have noticed that even when using a lightning-fast Internet connection, it takes a few beats, enough time to drum your fingers, for web pages to load. It’s likely because of online advertising, which bogs down your browser, drains your battery and jacks up mobile charges — not to mention collects private data.

So it’s little wonder that the use of ad-blocking software grew 41 percent last year, with 198 million active users worldwide, according to a study conducted by Adobe and PageFair. This represents an existential threat to the $50 billion online advertising industry and has ignited a bitter feud between advertisers and developers of ad-blocking apps. On the sidelines, privacy advocates are pumping their fists for consumer choice while web publishers wring their hands over lost revenue.

The fight became public last month when Randall Rothenberg, the president and chief executive of the Interactive Advertising Bureau, lobbed several verbal grenades at developers of ad blockers during his keynote address to his group’s annual leadership meeting. He called them “an unethical, immoral, mendacious coven of techie wannabes.” His venom was directed particularly at for-profit ad blockers who, for a fee, will unblock advertisers who meet certain standards of nonintrusiveness. Rothenberg called the practice “extortion.”

Ad blockers fired right back. “We are as motivated to protect consumers as advertisers are to abuse them,” said Roi Carthy, the chief marketing officer for Shine, an Israeli company that recently began offering ad-blocking software to wireless carriers, which are increasingly weary of the burden data-intensive ads place on their networks. Heretofore, ad blockers were mainly sold or given away to individuals. “This is a holy war for us,” Mr. Carthy said.