Some of the biggest sites on the internet have a message for the Federal Communications Commission: Messing with net neutrality means messing with Cyber Monday.

In a letter sent to the FCC, Twitter, Reddit, Tumblr, Airbnb, and some 200 other companies and business groups urge the commission to scrap its plan to eliminate federal net neutrality rules, which prevent internet service providers (ISPs) from manipulating data delivered to its customers. The rules prohibit ISPs from slowing down or speeding up the delivery of data from certain sites or blocking content altogether.

Were the FCC to gut federal net neutrality protections, critics warn, it could establish ISPs as the internet’s gatekeepers with the power to harm startups and other online businesses and services as they please.

“Without these rules, internet service providers will be able to favor certain websites and e-businesses, or the platforms they use to garner new customers, over others by putting the ones that can pay in fast lanes and slowing down or even blocking others,” the letter reads. “Businesses may have to pay a toll just to reach customers. This would put small and medium-sized businesses at a disadvantage and prevent innovative new ones from even getting off the ground. An internet without net neutrality protections would be the opposite of the open market, with a few powerful cable and phone companies picking winners and losers instead of consumers.”

On Dec. 14, the FCC will vote on a proposal to eliminate the net neutrality rules established in the 2015 Open Internet Order. FCC Chairman Ajit Pai, a Republican appointee of President Donald Trump and the proposal’s most vocal supporter, claims the rules against blocking content, throttling content, and “paid prioritization” (i.e., increasing data delivery speeds for companies who pay for better service) have stifled the internet provider industry and limited infrastructure investment as a result.

In their appeal to the FCC, the letter’s signatories note that “Americans spent almost $3.5 billion online on Cyber Monday” in 2016, while total online sales hit $400 billion last year, according to the U.S. Census Bureau.

The letter to the FCC is one part of a massive grassroots effort to keep the Republican-controlled FCC from gutting net neutrality rules. Internet freedom activists plan to launch a nationwide protest outside Verizon stores across the United States on Dec. 7. And a White House petition calling on Pai to resign racked up more than 84,000 signatures in less than a week.

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