Millions of websites - including Sky News, The Associated Press and Buzzfeed - will now be able to block artificial intelligence (AI) bots from accessing their content without permission.
The new system is being rolled out by internet infrastructure firm, Cloudflare, which hosts around a fifth of the internet. 
Eventually, sites will be able to ask for payment from AI firms in return for having their content scraped.
Many prominent writers, artists, musicians and actors have accused AI firms of training systems on their work without permission or payment.
In the UK, it led to a furious row between the government and artists including Sir Elton John over how to protect copyright.
Cloudflare's tech targets AI firm bots - also known as crawlers - which are programs that explore the web, indexing and collecting data as they go. They are important to the way AI firms build, train and operate their systems.
So far, Cloudflare says its tech is active on a million websites.
Roger Lynch, chief executive of Condé Nast, whose print titles include GQ, Vogue, and The New Yorker, said the move was "a game-changer" for publishers.
"This is a critical step toward creating a fair value exchange on the Internet that protects creators, supports quality journalism and holds AI companies accountable", he wrote in a statement.
However, other experts say stronger legal protections will still be needed.
' Surviving the age of AI '
Initially the system will apply by default to new users of Cloudflare services, plus sites that participated in an earlier effort to block crawlers.
Many publishers accuse AI firms of using their content without permission.
Recently the BBC threatened to take legal action against US based AI firm Perplexity, demanding it immediately stopped using BBC content, and paid compensation for material already used.
However publishers are generally happy to allow crawlers from search engines, like Google, to access their sites, so that the search companies can in return can direct people to their content. 
Perplexity accused the BBC of seeking to preserve "Google's monopoly". 
But Cloudflare argues AI breaks the unwritten agreement between publishers and crawlers. AI crawlers, it argues, collect content like text, articles, and images to generate answers, without sending visitors to the original source—depriving content creators of revenue. 
"If the Internet is going to survive the age of AI, we need to give publishers the control they deserve and build a new economic model that works for everyone," wrote the firm's chief executive Matthew Prince. 
To that end the company is developing a "Pay Per Crawl" system, which would give content creators the option to request payment from AI companies for utilising their original content.

Millions of websites to get 'game-changing' AI bot blocker

Cloudflare has rolled out a new AI bot blocker system to prevent AI firms from scraping content without permission, affecting sites like Sky News and The Associated Press. The system allows publishers to request payment from AI companies for using their content, addressing concerns over copyright and fair compensation. The move has sparked legal debates, including a UK dispute between the government and artists like Sir Elton John.