How is the rating calculated?
The extension checks the security headers and counts how many of them are present, and how many correct values they contain. For each missing header or unsafe value, the total score is reduced by a predefined value.
The score is then converted from a scale of 1 to 100 to a scale of A to F, and displayed in a pop-up window. The score is recalculated each time a separator is reloaded.
On tabs where the security level cannot be calculated (eg in a new tab), the extension displays a status of "Unknown" and "?".