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On Thursday, activists and tech companies will hold a final internet-wide day of action to help preserve net neutrality.

Dec. 10 is the deadline for Congress to vote on the Congressional Review Act (CRA), which has the potential to reverse the FCC's repeal and preserve net neutrality.

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Ahead of that deadline, thousands of internet users are joining together to sign an open letter to Congress in support of net neutrality. Companies including Tumblr, Etsy, Postmates and Sonos, as well as celebrities like Evangeline Lily and Tom Morello are also backing the effort.

The FCC's decision to repeal net neutrality rules has sparked protests from big companies and average people alike. Net neutrality is the principle that all traffic on the internet should be treated equally, regardless of whether you're checking Facebook, posting pictures to Instagram or streaming movies from Netflix or Amazon. Supporters of net neutrality say the internet as we know it may not exist much longer without the protections, but critics have said the rules stifled investment.

A CRA resolution passed the Senate in May. If it passes both houses of Congress, it still has to be signed into law by President Donald Trump to officially turn back the repeal.