In Firefox I use this extension for the same purpose https://addons.mozilla.org/en-US/firefox/addon/work-offline-page-only/?utm_source=addons.mozilla.org&utm_m

In Firefox I use this extension for the same purpose https://addons.mozilla.org/en-US/firefox/addon/work-offline-page-only/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search https://addons.mozilla.org/en-US/firefox/addon/work-offline-...