This policy controls the ability of a document to use the
swap values of the font-display
CSS property. If the policy is disallowed for the current document, then any elements
with a font-display that is not
optional will be
It's annoying for users when fonts take a long time to load, rendering a page unreadable
even though the text is available ('blocking'). Not quite as bad, but still a jarring
user experience, is when a fallback font is used and the element is rerendered in the
webfont when it is available ('swapping'). Disabling the
font-display-late-swap policy prevents both of these effects by giving the
webfont a very small window of opportunity to load, and if it doesn't load in time,
simply not using it at all and continuing to use the fallback instead.
How to apply this policy
Send the following HTTP header to control the
and disallow it on all origins:
Feature-Policy: font-display-late-swap 'none'
Does it work?
Currently Firefox, and Chromium based browsers, such as Google Chrome, Samsung Internet,
and Opera, are the only user-agents to support Feature Policy. The minimum version that
correctly recognises the
font-display-late-swap policy is: