While tracker-blocking in today's sense would have made no sense, there certainly was ad-blocking and cookie-blocking before the 2000s. AdSubtract advertised i

While tracker-blocking in today's sense would have made no sense, there certainly was ad-blocking and cookie-blocking before the 2000s. AdSubtract advertised it's ability to block doubleclick.com cookies in March of 2000: https://www.computerworld.com.au/article/91102/adsubtract_blocks_ads_cookies/ https://www.computerworld.com.au/article/91102/adsubtract_bl... The article also mentions Siemens' WebWasher product which blocked cookies. Other cookie-blocking products were released in the same time period.