AdGuard DNS Stopped Blocking Ads on iPhone? Here's What I Think

I recently stumbled upon a post detailing a frustrating situation: AdGuard DNS, after working flawlessly for nearly a year, suddenly stopped blocking ads on an iPhone. The user specifically mentioned using a DNS-over-HTTPS (DoH) profile. This got me thinking about the various reasons why a seemingly stable DNS-based ad-blocking setup might fail, especially on iOS.

Let's explore the potential culprits and troubleshooting steps, keeping in mind the nuances of iOS and DNS configuration.

Understanding Why DNS Blocking Can Fail

Before diving into iPhone-specific issues, it's crucial to understand the general principles behind DNS-based ad blocking and its potential weaknesses.

1. Blocklist Updates and Coverage

• Blocklist limitations: AdGuard DNS, like other DNS-based blockers, relies on blocklists – curated lists of domains known to serve ads and trackers. If a new ad network or domain emerges that isn't yet included in the blocklists, ads from that source will slip through.
• Blocklist maintenance: Blocklists require constant maintenance. Ad networks are always evolving, finding new ways to deliver ads. If AdGuard's blocklists haven't been updated recently, or if the specific lists used by the user are outdated, the effectiveness of the blocking will diminish.

2. DNS Propagation and Caching

• DNS caching: DNS records are cached at various levels – on the device, by the ISP, and by public DNS servers. If a previously unblocked domain is added to a blocklist, it might take some time for the updated information to propagate through the DNS system and for cached entries to expire. This delay can result in ads continuing to appear even after the blocklist is updated.

3. Circumvention Techniques

• Domain cloaking: Ad networks employ various techniques to circumvent ad blockers. One common method is domain cloaking, where ads are served from domains that appear to be legitimate content providers. This makes it difficult for blocklists to accurately identify and block ad-serving domains without also blocking legitimate content.
• Dynamic ad serving: Another technique is dynamic ad serving, where the ad server dynamically generates unique subdomains or URLs for each ad request. This makes it challenging for blocklists to keep up with the constantly changing ad infrastructure.

4. HTTPS and Encrypted DNS

• DNS-over-HTTPS (DoH): While DoH enhances privacy by encrypting DNS queries, it doesn't inherently improve ad blocking. It simply prevents eavesdropping on DNS requests. The effectiveness of ad blocking still depends on the underlying blocklists and the ability to resolve ad-serving domains.
• HTTPS Everywhere: Most websites now use HTTPS, which encrypts the content of the web page. This prevents ad blockers from directly inspecting the content to identify and block ads. DNS-based blocking remains effective because it operates at the domain level, before the HTTPS connection is established.

Potential Causes on iOS for AdGuard DNS Stopping

Given the general principles above, let's focus on potential causes specific to iOS that might explain why AdGuard DNS suddenly stopped working.

1. iOS Updates and Configuration Profile Issues

• iOS updates: iOS updates can sometimes interfere with configuration profiles, including those used for DNS settings. An update might inadvertently disable or corrupt the profile, causing the device to revert to the default DNS servers provided by the ISP.
• Profile corruption: Even without an iOS update, configuration profiles can occasionally become corrupted. This might be due to a software glitch, a conflict with another app, or simply a random error.
• Profile removal: It's possible, though less likely, that the user accidentally removed the AdGuard DNS configuration profile. This would immediately disable the custom DNS settings and revert to the default ISP DNS.

2. Network Connectivity Changes

• Switching networks: When switching between Wi-Fi networks or from Wi-Fi to cellular data, the device might not always properly re-apply the DNS settings from the configuration profile. This is more likely to occur if the profile is not properly configured or if there are conflicting DNS settings on the network.
• Captive portals: Public Wi-Fi networks often use captive portals, which require users to agree to terms of service before accessing the internet. Captive portals can sometimes interfere with custom DNS settings, forcing the device to use the network's default DNS servers.

3. Battery Optimization and Background App Refresh

• Aggressive battery optimization: iOS has aggressive battery optimization features that can restrict background app activity. While AdGuard DNS doesn't rely on a background app (since it uses a configuration profile), these features might still indirectly interfere with the DNS resolution process.
• Conflicting VPN settings: Some VPN apps might conflict with the AdGuard DNS configuration profile. If a VPN is active, it might override the DNS settings specified in the profile, causing the device to use the VPN's DNS servers instead.

4. Changes to AdGuard DNS Servers

• Server issues: Although rare, it's possible that AdGuard DNS experienced a temporary server outage or technical issue. If the DNS servers were unavailable, the device would fall back to the default ISP DNS, resulting in ads appearing.
• IP address changes: AdGuard DNS might have changed the IP addresses of its DNS servers. If the configuration profile uses outdated IP addresses, the device won't be able to connect to the DNS servers, and ad blocking will fail.

Troubleshooting Steps

Based on the potential causes, here's a breakdown of troubleshooting steps to address the issue of AdGuard DNS suddenly stopping working on an iPhone:

1. Verify the Configuration Profile

• Check installation: Go to Settings > General > VPN & Device Management. Ensure that the AdGuard DNS configuration profile is installed and listed.
• Profile details: Tap on the profile to view its details. Verify that the DNS server addresses are correct and match the ones provided by AdGuard DNS. If you're using DoH, confirm the DoH server address is accurate.
• Reinstall the profile: If the profile appears corrupted or if you're unsure about its integrity, delete it and download a fresh copy from AdGuard's website or configuration tool. Follow the installation instructions carefully.

2. Check Network Settings

• Wi-Fi settings: If you're using Wi-Fi, go to Settings > Wi-Fi, tap on your Wi-Fi network, and scroll down to the DNS section. Ensure that the DNS is set to "Automatic" or that the custom DNS servers specified in the configuration profile are listed.
• Cellular settings: Unfortunately, iOS doesn't allow you to manually configure DNS settings for cellular data. In this case, the configuration profile is the only way to enforce custom DNS settings.

3. Restart and Reset

• Restart the iPhone: A simple restart can often resolve temporary software glitches that might be interfering with the DNS settings.
• Reset network settings: If restarting doesn't help, try resetting the network settings. Go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. This will clear all saved Wi-Fi passwords, VPN settings, and DNS configurations, so you'll need to reconfigure them.

4. Clear DNS Cache

• Safari history and website data: Clearing Safari's history and website data can help to clear any cached DNS records that might be causing issues. Go to Settings > Safari > Clear History and Website Data.

5. Check for iOS Updates

• Software update: Ensure that your iPhone is running the latest version of iOS. Apple often releases updates that fix bugs and improve system stability, which might indirectly resolve DNS-related issues.

6. Disable Conflicting Apps

• VPN apps: If you're using a VPN app, try disabling it temporarily to see if it's conflicting with the AdGuard DNS configuration profile. If disabling the VPN resolves the issue, you might need to adjust the VPN settings or choose a different VPN provider.

7. Test with a Different DNS Server

• Temporary switch: To rule out the possibility of an issue with AdGuard DNS servers, try switching to a different DNS provider temporarily, such as Cloudflare 1.1.1.1 or Google Public DNS. If ads are blocked with a different DNS server, it suggests that the problem might be with AdGuard DNS.

8. Contact AdGuard Support

• Support forums: If you've tried all the troubleshooting steps and the issue persists, consider contacting AdGuard support for assistance. They might be able to provide more specific guidance based on your configuration and the symptoms you're experiencing.

Alternative Ad Blocking Methods on iOS

If you're unable to resolve the issue with AdGuard DNS, or if you're looking for alternative ad-blocking solutions, here are a few options for iOS:

1. Safari Content Blockers

• 1Blocker: 1Blocker is a popular content blocker for Safari that allows you to block ads, trackers, and other unwanted content. It uses a combination of blocklists and custom rules to filter content.
• AdGuard for Safari: AdGuard also offers a Safari content blocker that works similarly to 1Blocker. It's a free app that provides comprehensive ad blocking for Safari.

2. VPN-Based Ad Blockers

• AdGuard Pro: AdGuard Pro is a paid app that provides system-wide ad blocking using a local VPN. It filters all network traffic, blocking ads in all apps and browsers.

3. Brave Browser

• Built-in ad blocking: Brave Browser is a privacy-focused browser with built-in ad blocking and tracking protection. It blocks ads by default, without requiring any additional configuration.

My Take on the Situation

Based on the information provided, my initial suspicion is that an iOS update or a network change might have interfered with the AdGuard DNS configuration profile. It's also possible that the user accidentally removed the profile or that there was a temporary issue with AdGuard DNS servers. Regardless of the specific cause, I recommend following the troubleshooting steps outlined above to diagnose and resolve the issue.

While DNS-based ad blocking is generally reliable, it's not foolproof. Ad networks are constantly evolving, and ad blockers need to adapt to stay ahead. It's important to stay informed about the latest ad-blocking techniques and to be prepared to troubleshoot issues when they arise.

In the long run, a multi-layered approach to ad blocking is often the most effective. This might involve using a combination of DNS-based blocking, content blockers, and a privacy-focused browser like Brave. By combining different techniques, you can significantly reduce the number of ads you see and improve your overall browsing experience.

It's also worth considering supporting the developers of ad blockers by purchasing premium versions or making donations. This helps to ensure that they have the resources to continue developing and maintaining their products.

Ultimately, the best ad-blocking solution is the one that works best for you. Experiment with different options and find the combination that provides the best balance of effectiveness, performance, and ease of use.