Available for Digital Ad use. Available for Desktop use. Neue Helvetica Thai Bold Italic.

And here's another one to a Wikipedia article about the usage share of the different operating systems. This will also take some load off you server even though serving fonts isn't such a big deal.Here's a link to a site with some of the fonts that come pre-installed with different operating systems. Unfortunately Arial Narrow isn't included in iOS but, since both Helvetica and Helvetica Neue come pre-installed in all Apple devices, you wouldn't have to worry too much about it.Your font stack could be something like font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif and you'd be covering the most common devices and operating systems (except for Android which I think doesn't come with any of those two font families).Keep in mind this is far from ideal in most cases but would allow you to avoid licensing costs and reduce the time it takes for your website to load (since it will not be downloading fonts). It comes pre-installed in (almost?) every Windows version and also Apple devices.

Helvetica Neue Font Dafont