"noentry" is the video file Jay discovered on his laptop's hard drive that provides the content he reveals Entry #29. The contents of the video occupy from 00:25 to 01:03 on the video. The video involves someone — presumably Jay or Alex — running through the forest at Rosswood Park. It ends at the tunnel we see in Entry #49, where Alex kills someone following him, presumably because he thinks it is Jay. It was originally believed that this video hinted that Alex may have been killed himself. After the publishing of Entry #49, the common theory was that this video foreshadowed and showed the aftermath of Alex's killing of "Bruce."
Meaning of filename
Jay states only that the file is named "noentry," and does not give a file extension (such as .wmv, .mp4, .avi, etc) that would indicate what type of video file it is. This may or may not mean anything at all, since Jay may simply have not given it, as it is ultimately unimportant. However, if Jay did find the file without an extension, it would lend value to the theory that Jay was trying to hide the contents of this file prior to the events of Entry #52.
The name "noentry" itself could refer to multiple things:
- The phrase "no entry," meaning "keep out": Possibly as a warning to Jay's future self to stay away from the tunnel.
- The phrase "no entry," meaning "not an entry": Possibly Jay was never intending us to see this.
- The phrase "no entry," meaning "exit only": Possibly a threat to Jay that he should stop pursuing his investigation, or he might end up dead.
As recent entries have demonstrated increased importance of the tunnel itself, including the possibility of it being a kind of gateway, the first explanation is currently the most likely one.
As of July 2012, speculation on the unFiction forum points to this entry being outside of the actual timeline of the series or perhaps even non-canonical.