Apps for VPN on iOS already come in a bunch: some free, some paid, with all sorts of features you may (or may not) want. On the other hand, applications that simply block connections to certain domains, without having to route their connection to an external server are much rarer and exactly this is the proposal of Lockdown.
Developed by Duet Display creator Rahul Dewan and former iCloud engineer Johnny Lin, Lockdown is a free application that offers itself as the first open-source secure firewall for your iPhone or iPad. With it, you can block connections to any domain on your device, thus preventing companies like Facebook, Google or many others from tracking you over the internet or your device being used as a cryptocurrency miner.
Lockdown works simply: Just activate its function on the home screen and configure the list of blocked domains the app already has a default profile and several suggestions that can be blocked right away, and you can add any other domains you want. The operation of the app extends to all aspects of iOS, not just browsers.
Because it is open and with its code available on GitHub, the insides of the application can be checked by anyone interested in exploring its operation. It is good to note that even if you use iOS VPN APIs, Lockdown is not a VPN: It does not send your browsing data to an external server, processing all lock on the device itself which is much more quiet for your privacy.
In addition, the developers claim that your browsing may get faster, as multiple connections and heavy plugins are disabled right away when you load a page or app. Lockdown can be downloaded for free from the App Store, and its developers promise versions for macOS, Windows and Android in the near future, plus a paid version with VPN included.