SOPA and PIPA are the two internet privacy bills currently under consideration by the U.S. Congress with similar goals and provisions but certain key differences.

Both the Stop Online Privacy Act and Protect IP Act bills are aimed at stopping illegal downloading and other forms of web piracy, but here's four things that distinguish the two from one another:

1. Who will be voting on them: SOPA arose out of the U.S. House of Representatives, while the U.S. Senate is behind PIPA. The Republican-led House has different prevailing views on web privacy than does the Democratic Senate. SOPA is slated to return to markup by the House Judiciary Committee next month, while the Senate is slated to hold a procedural vote to begin debate on PIPA Jan. 24.

3. How much support they have in Congress: As of Jan. 17, SOPA has a total of 31 House cosponsors attached to it, out of 435 Representatives. That means only about 7.1 percent of House members support the Stop Online Privacy Act. Meanwhile, PIPA had a total of 40 Senate cosponsors on Jan. 17, out of 100 Senators. That amounts to 40 percent of the Senate supporting the Protect IP Act. In other words, PIPA has much more support in its respective house of Congress than SOPA does. 

2. How extreme they are: SOPA is the more extreme bill, as its controversial provisions would extend to any site committing or facilitating copyright infringement, while PIPA would only extend to sites with no significant use other than copyright infringement, as PC World has reported. Though this may sound like an issue of semantics, the difference is vast, as SOPA could impact any site that has even one instance of copyright infringement. That concept has brought the ire of everyone from Google to Wikipedia to the American Civil Liberties Union, all of which are concerned that the bill could lead to the wholesale shutdown of major sites and online communities like Facebook, Yahoo or Twitter simply because one of their users posted copyrighted material. PIPA is more narrow in that it would only impact sites that do little more than facilitate piracy, like the perennial scapegoat, Europe's ThePirateBay.

4. How popular they are: Well-informed web privacy wonks and major web giants are pretty much unequivocably against both SOPA and PIPA. But the backlash against SOPA has been the strongest. Web sites from Wikipedia to Boing Boing went dark Wednesday to protest laws that would restrict internet freedom. But SOPA has received the most grief, as the event became known as the SOPA Blackout, and most information about the protest contained more prominent critiques of the House legislation rather than the Senate bill.