From most solid/hardest, to least solid/softest (Note that promos and the like do not count for this scale):
Completely Solid Fourth Wall
- This Is Reality holds sway; within the four walls of the series, there is no direct acknowledgment of the viewer. (Lampshade Hangings, some degree of Genre Savvyness is allowed, but the Fourth Wall remains entirely intact).
- Mockumentaries and the like: There are cameramen who the actors acknowledge, but This Is Reality still holds sway.
Visible Fourth Wall
- Soliloquies, Asides, and the like, as long as the audience is not directly acknowledged. The characters behave as if they were characters in a story, but they don't know who might be watching. (You talk to the audience in a soliloquy, yes, but only because the conventions of the theater say that doing so means that you're actually just thinking out loud at the audience.)
- Leaning on the Fourth Wall
- Aside Glance/Comment
Semipermeable Fourth Wall
- A Narrator (but not a Viewpoint Character) who speaks directly to the audience, but whom the characters do not know about; but only if the narrator's announcements amount to more than "Meanwhile", "see Issue #7", or other scene setting.
- Fourth-Wall Mail Slot: where, outside of the plot, the characters respond, in character, to reader mail or reader content — if it is the only break in the fourth wall.
- And Knowing Is Half the Battle: a segment of the show where characters often lecture directly to the audience, sometimes acknowledging the unrealism of that episode's events.
- From Beyond the Fourth Wall: The creator of a work, the audience, or you, personally, interact with characters (in a way that isn't Audience Participation). Such as by lending the characters a boat, or money. Can happen in reverse too.
- Fourth-Wall Observer: One character has full Medium Awareness, and the others write it off as him/her being insane.
- In a video game, the characters are aware of the context of the game just enough to explain a concept of the game to the player, but do so within the context of the story. Common in Justified Tutorials.
- Clear Breaking the Fourth Wall happens, but at other times, everything works as if the characters are not aware of being fictional; the breakages are basically implied not to be canon, even though they may happen in the middle of the normal action.
Nonexistent Fourth Wall
- Medium Awareness: the characters may directly acknowledge the mechanics of their medium and/or that this is just a show, but these acknowledgments don't actually affect the plot and/or the characters never acknowledge their fictionality.
- Full No Fourth Wall: The characters acknowledge their fictionality directly.
- Noticing the Fourth Wall: The characters become aware they are fictional in the most terrifying way possible; the knowledge that they're only real in someone's imagination and will cease to exist when the story ends is used for existential horror.
- The Fourth Wall Will Not Protect You: Things inside the story, we are warned, can attack the reader.
- Mind Screws sometimes goes beyond No Fourth Wall, to imply such things as the viewer being a fictional character, so this entry is for them.
No examples; there are plenty of subtropes for them.
- Well, maybe a brief comparison of Bob and George and 1/0, to explain how the scale works:
- The characters of Bob and George know they're in a Web Comic, but it only sometimes directly impacts the plot, and the characters' actual existence is never in question.
- In 1/0, Medium Awareness is the main plot, and the characters themselves acknowledge and debate their possible fictionality/nonexistence.