A setting that only governs what has not happened yet
The security level is a browser setting that decides which classes of content are permitted to run. The content of this card is not which level to pick. It is when. A setting governs rendering that has not happened yet, and content already parsed and already executed is not retroactively unexecuted when a slider moves.
Stated plainly: if a page has loaded and run, lowering its permissions afterwards changes the next page and not that one. The tab still holds whatever state was created. Anything that ran, ran. This is how settings behave everywhere, and it is only interesting here because the ordering is easy to get backwards under mild impatience.
So the condition is a statement about sequence. At the moment the first page from the address renders, the browser is already at the level you intended. Not shortly afterwards. Not once you have seen what the page appears to need. The window in which this card can be true is closed by the first render, and it does not reopen.
Where the level comes from
The browser came from the Tor Project is the only card underneath this one, and it supplies a setting that means what it says. The level is not an external fact you can measure. It is a value the program holds, reported back through the program's own interface, and both halves of that are the software behaving.
A build that is not the published build can display any level it likes while rendering by another rule, and there is no way to notice from the chair. That is why provenance sits above this card rather than beside it. How to read a card describes what an upstream edge is claiming.
Nothing else feeds this. It does not need the network, the clock, or an address to exist. That makes it one of the few conditions on the map that can be settled entirely offline, before anything else in the stage is attempted.
What renders too early can never be un-rendered
Two cards depend on this one, and they fail differently enough to take separately.
The browser doing this does nothing else depends on it because containment is only worth having if the contained thing is limited in what it can do. Separating a browsing context reduces what can be joined across contexts. It does nothing about what can happen inside one, so a context with the widest capabilities is a boundary drawn around a larger thing.
You can tell a mirror from a copy of the market depends on it more directly, and this edge carries the real consequence. That card is about telling apart two addresses that render identically. The comparison is performed by looking at a rendered page, and if the page renders with the widest capabilities available, the thing you are comparing had the maximum opportunity to be whatever it wants. The level decides how much of that page is a document and how much of it is a program.
| Cannot hold | The reason it cannot |
|---|---|
| The browser doing this does nothing else | Containment limits what crosses between contexts, not what happens inside one, so the worth of the boundary depends on what was permitted inside it. |
| You can tell a mirror from a copy of the market | The comparison runs against a page that has already rendered. Rendering at a level you did not choose means the first look at an unknown string happened on terms the string set. |
| The account name is used nowhere else | Inherited through the card above. A name is committed to whichever place you decided was right, and that decision was made by reading a rendered page. |
There is a second reason the ordering matters, unrelated to anybody attacking anything. Changing the level after a page has loaded leaves a page in a state you did not watch it enter, half under one set of rules and half under another. Anything concluded from looking at it afterwards is a conclusion about a mixture.
The order people actually do it in
The common sequence runs: open the browser, paste the string, wait, look at what appears, decide the level should have been different, change it, reload. The reload is doing the work people believe the change did. With it, the page has still been fetched once at the original level, and that fetch happened.
On screen the whole thing is quiet. Nothing says a setting was applied late. Nothing indicates the first render used different rules from the second. The browser has no reason to mention it, because from its point of view nothing unusual took place.
The confusion lands later and lands on the setting itself. People conclude the level does not do anything, because they set it and the page looked the same. It looked the same because that page had been fetched before the setting reached its current value. The setting worked, applied to the future, which is the only thing it was able to govern.
Reading the level back on a blank tab
Open the security settings with nothing loaded, or with a blank tab in front of you, and read the level back off the interface. Then close the settings. Then paste. That order is the whole of the check, and it costs a few seconds at the least busy moment of the session.
- A pass
- You read the level while nothing from the address had been fetched, the value shown was the value you intended, and you did not change it again later in the same session.
- A fail
- You read the level after a page had loaded. Or you changed it after seeing what a page seemed to want. Or you cannot say what the level was at the instant of the first render.
None of that involves opening any address, and it should be done where none is loaded. That is a property of the check rather than a limitation of it.
This card is cheap and it stays true. Once the level is set and read back it holds for that browser until something changes it, which makes it one of the few conditions here that is finished before anything has started.
Not a ruling about which level
This is not an argument that one level is right for everybody, and no level is named here as correct. Readers accept different trade-offs and the map does not settle that for them. The adjacent thing it gets confused with is the choice itself, which is a decision. This card is only about when the decision is in force.