The dirty secret of the VPN industry is that most VPNs leak.
One in-depth study found that 84% of VPNs will leak your IP address.
In other words, many of the VPN services that market themselves as privacy and security solutions are in fact leaking your IP address and/or DNS requests. These leaks leave you exposed, which in turn could put you in a dangerous situation depending on your circumstances and online activities.
Also concerning is the fact that many VPNs have broken features. This is often the case with “kill switches” that do not effectively block traffic or “IPv6 leak protection” that does not secure your IPv6 address. It only takes one leaked packet to expose your identity and activities.
In this guide we’ll cover two different levels of VPN tests:
- Basic tests – These are the tests that anyone can run. Simply connect to your VPN and then hit the testing sites. Unfortunately, these basic tests will not identify all leaks (such as brief reconnection leaks).
- Advanced tests – These tests require more technical proficiency to get everything setup correctly, but they will identify any leaks you may have with your VPN. ExpressVPN put together the best tools available for in-depth leak testing, which are open source and available on GitHub.
We’ll start with basic VPN test procedures to identify obvious problems.
Basic VPN tests
Below are basic steps for identifying:
- DNS leaks
- IP address leaks (IPv4 and IPv6)
- WebRTC leaks
With these basic tests, you are relying on the testing website to identify problems. But as we noted above, you may have leaks that the test website does not pick up, which is why the advanced tests are the best solution.
For basic tests, I like to use ipleak.net as a general all-in-one testing site (created by AirVPN) along with the different Perfect Privacy test tools.
Test for VPN leaks
To test for active leaks, simply connect to a VPN server and visit the test site. You are checking to see how the VPN performs when the tunnel is active and stable.
You can also simulate different interruptions to see how well the VPN does if network connectivity drops. For example:
- Connect to a VPN server and load ipleak.net in your internet browser.
- Manually interrupt your internet connection (disconnect the ethernet cable or WiFi) while the VPN client is running.
- Reconnect to the internet and also load a few different test websites to see if your VPN is leaking upon reconnection.
This will help you to identify obvious problems with your VPN, but it won’t definitively identify all leaks (see advanced tests below).
VPN test websites
Here are a few testing sites you can use to check for different leaks:
- ipleak.net (IPv4, IPv6, WebRTC, and DNS)
- Perfect Privacy Test tools (IPv4 and IPv6, DNS, WebRTC)
- ExpressVPN leak tests (IPv4, DNS, WebRTC)
- test-ipv6.com (IPv4 and IPv6)
- dnsleaktest.com (use extended test)
- BrowserLeaks WebRTC Test
- ipx.ac (IPv4, IPv6, WebRTC, DNS, browser fingerprinting and more)
Now let’s see what a VPN leak looks like.
Identifying VPN leaks
When you use the testing site ipleak.net, it is fairly easy to identify leaks and problems, especially when you are connected to a VPN server outside your country. Note, the WebRTC leak test will show local IP addresses (usually beginning with 10.xxx or 192.xxx or sometimes an alpha-numeric IPv6 address that is also local). These are not leaks, but rather your local IP addresses. If you see your real (Public) IPv4 or IPv6 under the WebRTC section, then these are indeed WebRTC leaks.
Below you can see that I redacted the IP addresses in red where I experienced leaks with a VPN Unlimited server in the UK.
With the test results above you find:
- IPv4 address from UK server, but my real IPv6 address below (leak).
- Local IP address on the left (redacted, not a leak), but my public IPv6 address on right (WebRTC leak).
- IP address (DNS) from VPN server on left, but my internet service provider’s IP address on the right (DNS leak).
Example with no leaks
Now here are the test results when connected to a Perfect Privacy server in Sweden. Note, in the screenshot below, I am using a multi-hop VPN chain, using servers in Frankfurt, Copenhagen, Calais, and Malmo. The last server in the chain (Sweden) corresponds to the tests below.
In the screenshot above you see:
- IPv4 and IPv6 addresses from the Perfect Privacy server
- Local IP addresses under WebRTC detection (no public IP addresses, no leaks)
- DNS addresses from Perfect Privacy servers (Perfect Privacy uses multiple, secure DNS resolves)
Note on locations: The various testing sites use international IP address databases (RIPE) for the location. These location databases are not always accurate and may be outdated. To determine the true location of any VPN server, you need to ping the server from different worldwide locations using the steps in this guide.
Advanced VPN tests
The best method for identifying VPN leaks is to create a testing suite for your operating system and then run a barrage of tests to analyze traffic for leaked packets.
Creating a testing suite to capture and analyze traffic can be somewhat complex depending on the operating system you are using. Thankfully, ExpressVPN recently decided to publicly release the testing tools they use to leak-proof all of their applications.
The leak-testing tools are free, open source, and available on GitHub here.
This level of testing should effectively identify any leaks with Windows, Mac OS, and Linux.
If you are serious about security and online anonymity, you will want to run your VPN through these advanced tests to identify any problems. In other words, don’t rely only on the basic tests described above.
Quick start – Check out the quick start guide to set up your test machines to identify leaks with your VPN service.
DNS leaks
The Domain Name System (DNS) is a system for converting URLs, such as restoreprivacy.com, into a numerical IP address, such as 205.251.197.66.
Without a VPN, this translation process is handled by your internet service provider (ISP). But this is quite problematic because your DNS requests are clear text logs of every website you visit. Internet service providers log these requests of their users. In the United States, the data can be sold to advertisers that want to target you based on your browsing history. In the UK and Australia, the data is recorded and stored for up to two years and is available to authorities for whatever they want to do with it.
A DNS leak occurs when these translation requests leak out of the VPN tunnel, exposing the IP address (and location) of your ISP, as well as your browsing history. Many VPNs do not provide adequate DNS leak protection, which means your DNS requests are still going to your internet service provider.
Testing sites:
- Perfect Privacy DNS Leak Test (This site seems to detect DNS leaks when other websites do not find problems. Below the tests results you can also find a detailed explanation of DNS leaks.)
- IP/DNS Test at ipleak.net (This is another DNS leak test tool that also includes IP address leak results.)
Connecting to a VPN server outside your country makes detecting DNS leaks easier. You can see above there are two DNS requests leaking out while connected to a VPN server in the United States.
A DNS leak does not expose your IP address, but instead the IP address and location of your internet service provider (which can be linked back to you). Additionally, this exposes your browsing history (DNS requests).
Solution to DNS leaks: Find a VPN that uses its own secured and encrypted DNS resolvers. Below are three VPNs that use only their own secure DNS resolvers and did not have any leaks that I could find:
- Perfect Privacy (based in Switzerland; read review)
- ExpressVPN (based in the British Virgin Islands; read review)
- VPN.ac (based in Romania; read review)
You can also manually configure your DNS requests to use other third-party options. Here’s a list of alternative DNS options from WikiLeaks.
IP address leaks (IPv4 and IPv6)
IP address leaks are a major problem that many VPN users aren’t aware of.
IP address leaks are especially problematic with IPv6 addresses because this is a globally unique address.
While many VPNs effectively block IPv6 addresses (see ExpressVPN), other providers offer full IPv6 support by giving you both an IPv4 and IPv6 address (see Perfect Privacy).
Test sites:
Solution for IP leaks: The best solution is to simply get a VPN that does not leak (see below).
Another option is to manually create firewall rules that block all non-VPN traffic, but this can be a hassle.
WebRTC leaks
A WebRTC leak test is important for anyone using Firefox, Chrome, or Opera browsers.
The WebRTC issue is essentially a vulnerability with the browser, not the VPN itself. This is why using a good browser is so important.
A WebRTC leak occurs when your IP address leaks out via WebRTC APIs. Here are three different WebRTC leak tests:
- Perfect Privacy WebRTC Test (This tool will test to see if you have a WebRTC leak, while also providing a detailed explanation of WebRTC leaks at the bottom of the page.)
- BrowserLeaks WebRTC Test (Another WebRTC test that works well, also includes helpful WebRTC information.)
- ipleak.net
Solution for WebRTC leaks: Follow the steps in this WebRTC guide to disable or block WebRTC in your browser.
You can also go with one of the two VPNs that offer full WebRTC leak protection:
VPN speed test
If you’re looking to test VPN speed, here are three options:
What affects VPN speed?
There are many factors affecting speed that you should consider when testing. Here are a few:
- Distance between you and the VPN server – This is usually the biggest factor affecting speed. The further the distance, the slower the speed.
- Number of users on the VPN server – With so many VPNs over-selling their services, “popular” VPNs often have overloaded servers which results in slow speeds and dropped connections. Look for a VPN that provides a server status page with real-time bandwidth information. Two examples of this are VPN.ac (see VPN Nodes Status at the top of the page) and Perfect Privacy’s server status page.
- Regional bandwidth restrictions – Many countries have poor bandwidth infrastructure, which will limit your speed, regardless of how fast your ISP or VPN server is. A few examples of this are Germany and Australia. Another regional consideration is how many people are online at a given time of the day. High usage times can slow down speeds for everyone.
- Internet Service Provider – No matter how fast a VPN server is, it won’t be faster than the speed provided by your ISP. The only exception to this rule is if your ISP is throttling (limiting) your bandwidth. They sometimes do this if you’re doing something they don’t like (such as torrenting). A VPN can potentially help with this issue by encrypting your connection and hiding your online activity from your ISP.
- Processing Power – Whenever you’re using a VPN, your computer is working in the background to encrypt and decrypt packets of information. This takes processing power. The faster your internet speed when using a VPN, the more processing power is needed. So even if your ISP and VPN are fast, your CPU may be limiting your full speed potential (but this mainly applies to very high speeds).
VPN malware tests
Malware embedded in mobile VPN applications is a major problem to be aware of.
There has been an explosion of various free VPN apps available in the Google Play and Apple Stores. Just like with other free products, such as Gmail and Facebook, the platform is monetizing the user by collecting and selling your data to third parties.
One study found that 38% of Android VPN apps contain malware! I have also confirmed the presence of malware in Android apps – see the VPN Master article.
Test for malware – To test for malware, simply upload the software file to VirusTotal. The database will scan the file using over 60 different Antivirus tests. While there is a chance for false positives, researchers define a malicious app as one having four or more positive test results.
VPNs that do not leak
There are two VPNs that I have found to do the best job of protecting users against leaks in all types of scenarios including, reconnections, network interruptions, and VPN crashes. These two VPNs offer the best built-in leak protection features:
- Perfect Privacy – Offers very advanced leak protection settings along with full IPv6 support, but it’s somewhat pricey at €8.95 per month.
- ExpressVPN – Offers advanced leak protection settings and a great selection of apps for different devices. The standard price is $8.32 per month, but you can get it for $6.67 per month with this discount (applied at checkout page).
Whichever VPN you decide to use, it’s a good idea to periodically check for leaks and other issues, especially after new updates.
I recently purchased a Netgear x6s AC 3000.
Netgears OpenVpn doesn’t connect. In order to enable it u have to create a Dynamic dns and use OpenVpn Connect to import your profile to connect. It doesn’t connect. There OpenVPN is only used to connect outside your network to your network.
Would you purchase a Asus router instead or use Vypyn VPN on the Netgear?
Hi Mark, I’m not too familiar with that router. Perhaps you could check out flashing it with a different firmware that would work better for you – see the VPN router guide.
Wish I would have found your article before, when I was seriously annoyed trying to figure out where exactly my leak was coming from. I use Nordvpn, and set it up on my router. As they don’t (yet) support IPv6, that was where the leak came from. I had to disable IPv6 (wan6) interface on my router, otherwise the IPv6 address was generated by ISP as VPN provider doesn’t support it. Official applicaiton will block IPv6 because of no support for it, but OpenVPN on router doesn’t (maybe there is a way to configure it to do so, though I’m not sure). As like DNS was the previous leak i had, which i had to configure wan interface by unchecking ‘use dns advertised by peers) and use primary and secondary dns of vpn provider, otherwise it would be a leak. As I also hard to disable WebRTC in firefox, but I prefer using Tor Browser when I dont have huge files to download (400kbps download speed would be too slow to download ~20GB) other than that, I everything is already now. I’ve used all testing sites you have in this article, as well as I’ve performed the advanced test @ github. Just wanted to say, thank you 🙂
Hi Daryn, happy to help. Disabling WebRTC is easy in Firefox via about:config – see instructions here.
Hi Sven
What do you think about privacy browsers, such as Epic? the tool has built-in VPN/proxy something – I’m not an expert but the browser has passed (i think so) tests from links you have shared. (DNS leak, ipvanish, penta…) please check if these tools are protected and trustworthy.
Hi Pepe, I’d opt for the Tor browser in combination with a VPN and the Tor network disabled. This is explained more in the browser fingerprinting article. I’ve read that Epic browser leaks (here and here).
I am using free TunnelBear VPN and so far it’s great. There are lots of infomation on the bussiness. It also passed Iv4P, DNS, IP, but it didn’t have Iv6P. Is that a problem? If so, why?
Hi CP, most VPNs do not support IPv6, which means you will only get an IPV4 address when you connect to a VPN server and they will block IPv6. For mobile devices, this can be a problem because we are moving toward IPv6-only mobile networks. For computers, this is not such a big problem… yet. But we’re slowly transitioning to IPv6.
Thank you for your reply. That explains why some websites crash whenever I use a VPN. I have to turn off so I could access IPv6 websites, which is a big inconvenience.
Do you know the difference between a proxy and a VPN? You’ve mentioned it that Opera has one, but it didn’t go into much detail how a proxy works.
Hi CP, the main difference is encryption, even though both allow you to hide your true IP address. A VPN, however, will offer a higher level of encryption, which provides more security and privacy protection. Some VPNs offer browser extension proxies as well, such as VPN.ac. There is also a difference in performance. A proxy will generally be faster than a VPN – again, because of encryption.
Is windscribe okay
I don’t think it is dangerous/malicious like many of the free VPN apps you find. Windscribe uses the “freemium” business model, giving users about 10 GB of free bandwidth, before they have to pay.
Hi Sven, can you suggest a number of good VPN to use within the UK? Thanks.
Hi Queen, if you are in the UK, I’d generally recommend avoiding UK providers. Any of the recommended providers on the best VPN page should work fine. I’ve tested all of them with European and American servers – if they are on the list they did well in testing.
Another good test you can find here: https://www.doileak.com/
I shall highly appreciate your feedback on IP HIDER PRO. I find that it passes all the leak tests – IP, DNS, Web RTC etc. Speed is also great. I am planning to buy it and hence need your assessment.
Thanks
Hi PB, I’m not so sure about that one. The website looks like it hasn’t been updated since 2016 and there is barely any information about the business, jurisdiction, or operating details of the company. These are red flags to me.
I have pure VPN and with a few exceptions I find it pretty good. I am not sure what it is related to, but there are some DNS leaks with it dependant upon the test. PureVPN seems to pass all tests you throw at it from your blog, except the DNS tests. It passed DNS leaks across 4 other web sites showing google in chile. However, on your DNS leak tets 4 of the listed addresses were not mine, but the IP of my service provider. What does that mean? I have not run into any blocked sites of yet, and have been using it for some time. I know that there are a few sites that rank it as pretty good, as not being in one of those 14 nations. I just wanted to know what those DNS leaks meant where they were not detected on DNS leak test or some others but were found on yours. Thanks.
Hi John. When you run a DNS leak test and see the IP address of your internet service provider, that means your DNS requests are leaking out of the VPN tunnel and being handled by your ISP. A DNS request is just a simple translation that converts a regular website URL into an IP address. Without a VPN, your ISP will handle all of these requests when you visit various websites. This is an easy way for ISPs to monitor and record every website you visit. It also is a privacy issue because when these requests are leaking it can be traced back to your location and internet service provider (and essentially you). So this is bad from a privacy standpoint.
The test results may vary depending on which testing website you are using, which VPN apps, operating system, settings, and other variables. You can manually change/configure your operating system to use some other DNS, but you definitely don’t want to be having these DNS leaks with your ISP. For a nice overview on the DNS issue, VPN.ac put together a good article here.
ive got hide.me VPN Android have you tested this vpn they have a windows version also its got good ratings in a few vpn reviews
Hi John, no I have not tested it yet – but hopefully in the next few months.
Have you tested 360 Total security Turbo VPN comes with 360 total security Windows
Hi John, no I have not tested it. But from what I can find all of the products you mentioned (360 Total Security and its Turbo VPN) are offered by Qihu 360 – a Hong Kong company. Looking at Qihu 360’s Privacy Policy, I find they are collecting extensive amounts of data from their users, including all browsing history, devices, and personal information. So from a privacy perspective, I would not personally stay away from this company and all of their products.
thanks for feedback i decided to use virus total the 360 security app android result scan was 4 out of 60 detected one being a trojan spy Jiangmin . opened my eyes a bit
Yep, lots of Android VPN apps contain malware and tracking. Good job testing it out with VirusTotal.
You particularly point out PureVPN which I had recently purchased. I have a knowledge of an average computer user.
I read that you can use the OpenVPN client and just use the PureVPN servers. This will essentially remove the PureVPN software from the equation. Would this solution work?
One troubling aspect I do encounter when I use Pure VPN is that it seems some websites block PureVPN server addresses because I guess their users are known for unscrupulous activity? I just want to maintain my privacy and security, that’s all.
Can you recommend anything I can do?
Hi Johnson, you can definitely use third party OpenVPN clients, but I suspect you will still have problems. The DNS leaks, for example, are a problem with the server network and the way it’s configured. When I pointed this problem out, PureVPN’s proposed using Google DNS – which gives Google your browsing history. The IP leaks are likely a network and software issue – but you can test it out to see. One great option is Viscosity, which works on Windows or Mac. You can try it free for 30 days, after that you’ll need to buy the license for $9 (lifetime). Free clients include Tunnelblick (Mac OS) and OpenVPN GUI (Windows).
Regarding blocked websites, you are correct – that’s usually caused by spammers using the VPN, and then those IP addresses getting banned. The only solution here is to find another server. You may want to cut your losses and go with another provider, but you can test out PureVPN with the third party clients first to see how well it works.
Hi Sven,
Regarding OpenVPN GUI, there are a few security-issues that have to be taken care of before you’re completely safe. First, there is the DNS-leak. To fix this, you need to add the following line to your openVPN-config file:
block_outside_dns
Second, when you use openVPN with windows10, you are leaking DNS data through the windows10 resolver. To fix this, you need to get this fix:
https://github.com/ValdikSS/openvpn-fix-dns-leak-plugin
also, don’t forget to add this line to your OpenVPN-config:
plugin fix-dns-leak-32.dll
for 32 bit system or
plugin fix-dns-leak-64.dll
for 64 bit system
After plugging the above leaks, test your OpenVPN against a good test-site like whoer.net. You should be able to get a 90% score now, even with a free service like vpnbook or similar.
Just my 2 cents, again. 🙂