NetGuard is amazing, really can't recommend it enough.

You can use it to specify which apps are allowed to use WiFi/data, and whether they're allowed to use all the time or only if screen is active. It also allows you to set a hosts file URL and update it with a single click. It has improved my battery life, I rarely see ads (both when using the browser and when using apps), and it force me to use old.reddit.com since reddit.com is blocked by my host file.

Default settings prevent posting to Imgur through their app. What other normal functionality does this break, and why?

imgur and reddit have become evil, so I wouldn't say it's surprising that their websites/apps stop working when you begin to block tracking and analytics. Both of these companies seem to go out of their way to break functionality for users that try to protect their privacy. I recommend you blame imgur rather than NetGuard.

Just tried it. It uses a VPN so you can't use it if you already use a VPN. :/

Without root there's no other way to route all traffic and android doesn't allow chained vpn's.

It's an excellent app, source code is on github, eventually ended up paying for it. There's far too many apps and system binaries dialing out, it's funny to watch in realtime. What's more amazing is how nothing breaks even when you lock down everything but the few things that need it. Blocking is fine grained and you'll have to scroll through a massive list if you choose to view system apps, but quite happy overall.

Main benefit of the paid option is pcap files. Free version does everything most will want. It's on fdroid.

If anyone came up with a list of domains, I'd gladly add them to my DNS server to block them. But I won't give up my VPN.:/

I run pihole on a Raspberry Pi3 at home and you'd be wowed at the amount of dialling home all devices so, and metrics. With a network of Apple iPad/Mac, Windows and Android devices, it's over 25% of all DNS requests that I block.

Useless once you take your phone off WiFi of course, but still baffling the amount of metric abuse going on, and entirely without warning (am within the EU so concerned by it!)

Anyone know of a similar app for iPhone?

You can use Charles proxy to see all the traffic. There’s an iOS app but I highly recommend the desktop app. It helps for greater discovery.

Works for http/s only I believe.

Don't think such an app would be accepted by Apple. Why are using iPhone if you want ownership over your device?

This is a naive response I see given to iPhone users when they ask about how to get a certain feature. It’s obvious no research was put into this answer as a sibling comment to yours clearly helped out by suggesting Charles proxy which is now available natively on iOS.

Well, ‘VPN’ apps that are really ad blockers or data loggers are not allowed on the App Store.

One could argue that your response is naive;

NetGuard is a firewall which allows to allow/block traffic.

Charles proxy only allows you to see which connections are being made. They cannot be blocked, there is no firewall functionality. There is not a single app on the App Store that can behave like a firewall on an iOS device, and Apple would definitely not allow this.

So i personally think he has a point; Apple dictating what you may or may not do with your device, without giving you the possibility to opt-out, is not good. Apples "walled garden" has positive side effects of course, like for example hardly any malware on iOS devices versus a lot of malware/viruses on Android devices.

But still, there should be the ability to opt-out of this when accepting the risks. Without this ability it's much like a dictatorship...

Why would you buy a phone with Google’s Android if you want to block data collection?