The default sans-serif font in Firefox for Mac is Helvetica, but the default font for macOS is San Francisco. If you want to have your page use a system-looking

The default sans-serif font in Firefox for Mac is Helvetica, but the default font for macOS is San Francisco. If you want to have your page use a system-looking font, particularly if you're building an Electron app like Slack, you might want to get past the browser defaults and instead use the system defaults. I used macOS fonts in my example, but this applies to every platform.