Re-watching footage from 9/11, regardless of the anniversary, is undoubtedly eerie, but for some, remembering that terrible day is often necessary in order to pay tribute to those who lost their lives.
For others, especially a generation growing up in the post-9/11 world, watching the footage helps form at least a partial understanding of the attacks.
Technology was able to preserve the memory of the events, for better or worse. Now, the clips that were once only considered a dramatic memory of a tragic day have become a part of history.
The availability of video cameras and recording devices at the time made 9/11 possibly the most recorded tragedy in national history. Though 2001 pre-dates the widespread use of smartphones and cell phone cameras, there were many New Yorkers, and Americans in general for that matter, within arms-reach of a camcorder.
However, there is still little footage of the first plane flying into the North Tower of the World Trade Center, since few eyes were on the sky until it happened. There is also no footage of the plane crashing in Pennsylvania (the most widely seen footage is from after the crash), and there's little coverage of the crash at the Pentagon.
But the moment the second tower was hit is well documented. As many Manhattanites focused their cameras on the first tower burning, they witnessed United Airlines Flight 175 fly into the South Tower. The reactions, as can be heard in many of the videos below, were dramatic.
When the towers began to fall nearly an hour later, many had long been filming the incident, and news cameras were all over the scene.
With all eyes on New York -- a city that has long housed national media titans such as CNN, ABC, NBC and Fox News -- millions of Americans were exposed to the attacks in near real time. From impact to collapse, it was all captured and, for the most part, shown live on television sets throughout the country, and perhaps the world.
The coverage was so in-depth that sites such as the Internet Archive have collected enough footage to virtually replay the day.
We've also provided a number of videos from 9/11, which can be seen below.
WARNING: Some of the language in the videos below may not be suitable for all ages.