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Does a VPN Slow Down Internet? Usually, a Little

Two paper boats floating toward the same small harbor at dawn, one on a short straight channel and one on a longer loop around a lighthouse island, with an iPhone resting on the grassy bank

Usually a little. Why a VPN costs some speed, what changes how much, how to test it on iPhone, and the rare case where a VPN can be faster.

Marco Lee7 min read

Yes, usually a little. A VPN encrypts your traffic and sends it through an extra server before it reaches the site, which adds work and usually distance, so most connections get somewhat slower. How much depends on how far away the VPN location is, how busy its server is, the protocol and your network, so I’d pick a nearby location and check with a speed test, VPN off and then on.

Why does a VPN slow down internet speed?

Without a VPN, your iPhone reaches a site over your Wi-Fi or cellular network. With one, everything goes to the VPN server first. NIST describes a VPN as “a virtual network built on top of existing physical networks” (NIST), so it adds a step to the network you already have. That step costs speed in four ways:

  • Extra distance. Your traffic travels to the VPN server, then on to the site. Researchers who used a VPN to measure mobile networks named “latency added by going through the VPN” as one of its two costs, for example when the VPN “induces a circuitous route” (Kakhki et al., IMC 2015). Distance shows up in speed tests too: Measurement Lab says tests to a server inside your own provider’s network often score higher, partly because “the ‘distance’ traveled is generally shorter” (M-Lab).
  • Encryption overhead. Every packet is encrypted on your iPhone and decrypted at the server. NIST’s VPN guide says IPsec “can be computationally intensive, primarily because of encryption and decryption,” and that the few bytes encryption adds to each packet “might lead to fragmentation, which will reduce performance” (NIST).
  • A busy server. One VPN server works for many people at once. NIST describes busy remote access VPN servers handling many users’ connections on each processor, and warns that when such a server is overloaded, processing everyone’s data slows too (NIST).
  • The protocol. WireGuard, IKEv2 and OpenVPN build the tunnel in different ways. More on that below.

How much does a VPN slow down your internet?

There’s no fixed figure, and I’d be wary of anyone who promises one. One careful measurement comes from the 2015 study behind Northeastern University’s Wehe app (Wehe). The authors ran the VPN server on the same machine as their test server, which added “less than 2ms of latency.” In that best case, “for most applications, the difference in throughput with the VPN is 2% or less.” Skype’s traffic, with an average packet size under 300 bytes, lost more: 15% (Kakhki et al., IMC 2015).

That’s the cost of encryption with almost no detour. In everyday use, distance, a busy server and your network add to it, so your own on/off test, below, is the number that counts.

What changes how much a VPN slows you down

How far away the VPN location is

Every request goes to the VPN server and back, so a location on another continent makes each round trip longer than one in your own region. If you don’t need a particular country, I’d use the nearest location.

The protocol: WireGuard, IKEv2 or OpenVPN

iPhone has built-in support for “L2TP, IKEv2, and IPSec VPN connections” (Apple Support). IKEv2 belongs to the IPsec family: in NIST’s words, terms like “IPsec VPN” and “IKEv2 VPN” “all refer to IPsec-based VPN connections.” WireGuard is newer, “a minimalistic VPN implementation that is less complex than IPsec” (NIST).

The clearest speed claims come from WireGuard itself. Its site says it “aims to be faster, simpler, leaner, and more useful than IPsec” and “intends to be considerably more performant than OpenVPN” (WireGuard). Its performance page calls its own benchmarks “old, crusty, and not super well conducted,” and says WireGuard is still “edging out IPsec in some cases” (WireGuard). That’s the project’s own view, from tests on Linux computers rather than iPhones. I’d take it as a reason to try WireGuard first and let your speed test decide.

The network you’re on

A VPN rides on whatever network you’re using, so slow Wi-Fi or a weak cellular signal stays slow with the VPN on. Some networks also get in its way. NIST says the most common problem when setting up an IPsec VPN is a firewall “blocking the IKE ports UDP 500 and 4500,” and that routers or firewalls sometimes drop the fragmented packets a VPN’s extra bytes can cause, so the VPN works for a simple test “but not when an application is trying to use” it (NIST). On your iPhone, that looks like a VPN that won’t connect, or one that connects while apps stall.

Mobile networks can treat VPN traffic differently too. The researchers’ test app switched to another method when “the cellular provider blocks or differentiates against VPN traffic” (Kakhki et al., IMC 2015).

Does a VPN slow down Wi-Fi?

Not the Wi-Fi itself. The link between your iPhone and the router is the same with the VPN on; what changes is where your internet traffic goes after the router. If your internet is slow with the VPN off too, the VPN isn’t the cause. Why is my internet so slow on iPhone walks through the Wi-Fi, the provider and the site.

How to check if your VPN is slowing you down

  1. Stay in one spot, on one network. Moving rooms or switching networks between tests changes the result on its own. Pause big downloads and backups.
  2. Turn the VPN off, in its app or in Settings > General > VPN & Device Management (Apple Support).
  3. Run a speed test in Safari, such as Measurement Lab’s at speed.measurementlab.net. Note Download, Upload and Latency. M-Lab asks you to agree to a data policy that “includes retention and publication of IP addresses” (M-Lab Speed Test).
  4. Turn the VPN on, wait until it says it’s connected, and run the same test again.
  5. Run each one twice. Results drift: M-Lab notes that “A test conducted five minutes ago may show very different results from a test conducted twenty minutes ago” (M-Lab).

If latency jumps with the VPN on, distance is the first thing I’d change. If it barely moves but downloads drop, I’d try another protocol, then another location.

The VPN test on this site is a different check. It shows the IP address and network websites see, and looks for WebRTC and IPv6 leaks. It tells you whether the VPN is working, not how fast it is.

Does a VPN slow down internet on iPhone? How to keep it fast

The same costs apply on iPhone. What you can control:

  1. Pick the nearest location you can use. A short detour is the cheapest one.
  2. Switch protocols if your app lets you. I’d try WireGuard first, then IKEv2. If a network blocks or stalls one, the other may get through.
  3. Compare Wi-Fi and cellular. Do the on/off test on each. To test cellular alone, turn Wi-Fi off. If one network is slow with the VPN off as well, that network is the problem.
  4. Try another location if a usual one is slow today. A busy server slows everyone on it.

Can a VPN make your internet faster?

Rarely, and mostly in one case: your provider slows a particular kind of traffic. Wehe explains that providers “typically implement differentiation by looking into the data transferred to your device, and applying throttling based on what they see” (Wehe). Inside a VPN tunnel, the contents are “hidden from any shapers on the path,” which is why Wehe’s original 2015 method used VPN traffic as its unthrottled comparison (Kakhki et al., IMC 2015). When a provider throttles by recognizing an app, that app’s traffic can run faster inside the VPN.

The limits matter. A VPN can’t fix a slow network, and as above, some networks block VPN traffic or treat it differently. The same paper also mentions “unlimited” plans “with lower data rates after usage exceeds a certain cap” (Kakhki et al., IMC 2015). A VPN hides what your traffic is, not how much of it there is. To find out whether you’re being throttled at all, see is my internet being throttled.

Should I turn off my VPN to get better speed?

Only to test, or briefly for one task. If the on/off test shows the VPN is the slow part, I’d try a nearer location or another protocol before giving up the protection, especially on hotel, airport or café Wi-Fi. Should you keep a VPN on all the time covers when switching it off makes sense.

Where Mistero fits

Mistero doesn’t measure your speed, and it can’t make a slow Wi-Fi network or a slow plan faster. It’s a VPN, so it adds a step like any other; the on/off test above shows what that costs you.

What it gives you are the controls this post points to. You can “Connect to available VPN locations in one tap” and “Mask your IP address while the VPN is active,” and the 4.0 release added “protocol selection, and recommended or streaming-optimized routes where available” (App Store listing, read Nov 6, 2026). You can also “Turn on Kill Switch to help stop network traffic if the VPN disconnects.” More on Mistero VPN.

Sources

Pricing New subscribers can start a 3-day free trial. After the trial, the subscription renews automatically at $12.99 per week unless you cancel at least 24 hours before the trial ends, in Settings > [your name] > Subscriptions (Apple Support). There's also a one-time Lifetime purchase for $99.99. These are US App Store prices as of October 2026; the purchase screen shows the current price before you confirm.

Frequently asked questions

Does a VPN slow down internet speed?

Usually a little. Your traffic takes a detour through the VPN server and is encrypted on the way, and both cost some speed. A nearby VPN location keeps the detour short. To see what it costs you, run a speed test with the VPN off, then on, in the same place.

How much does a VPN slow down your internet?

There's no fixed figure. In a 2015 study with the VPN server right next to the test server, the VPN cost 2% or less of throughput for most apps' traffic and 15% for Skype's small packets. In daily use, the distance to the VPN location, how busy its server is and your network add to that, so test your own.

Can a VPN make your internet faster?

Rarely. If your provider slows one kind of traffic, like video, by recognizing what it is, a VPN hides that, so the traffic may get through at normal speed. A VPN can't speed up a slow Wi-Fi network, a weak signal or a plan that slows all your data after a cap.

Should I turn off my VPN to get better speed?

Only to test, or briefly for one task. If the VPN turns out to be the slow part, I'd try a closer location or a different protocol first, and keep it on when you're on Wi-Fi you don't control.
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