toolkit.legacyUserProfileCustomizations.stylesheets

[TCW]

So I just read that in FF69 that userChrome.css and userContent.css will
no longer work unless
toolkit.legacyUserProfileCustomizations.stylesheets=true. So what's
replacing userChrome.css and userContent.css in terms of customization?
I use those files *religiously* to keep users at my org from messing
with things they ought not. Are there plans to someday remove
toolkit.legacyUserProfileCustomizations.stylesheets altogether?

[Dave Royal]

userChrome.css and userContent.css are not being removed; this is being
done to speed startup. toolkit.legacyUserProfileCustomizations.stylesheets is
set automatically in Fx68 if you use them:
<https://www.ghacks.net/2019/05/24/firefox-69-userchrome-css-and-usercontent-css-disabled-by-default/>

You can replace userContent.css with a stylesheet added by a
webextension. It's documented under 'content scripts'.
There are also addons (Stylus, Stylish) which make it easy to add
userstyles; why would you use userContent.css?

Future use of userChrome.css is qualified here:
<https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/Tutorial/Modifying_the_Default_Skin>
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