Why your VPN is slow and how to speed it up: 4 checks, MTU, and what's normal

A slow VPN is the most common complaint after "it will not connect". Most of the time it is not the VPN itself but one of the causes below: a distant or overloaded server, weak Wi-Fi, the wrong packet size (MTU), or slow DNS. Go through four checks in order — they take about ten minutes. Written for the NvoVPN app, but most points apply to any VPN.

1. 1

   Measure the speed properly

   Run any speed test without the VPN, and note the result and the test server. Connect the VPN and run the same speed test against the same server. The difference is the tunnel's real cost. Normal for AmneziaWG is a loss of a few percent and a few milliseconds of latency. If speed fell several times over, keep going.

2. 2

   Change the server

   The automatic pick is the nearest server, but even that one can be busy. Choose another by hand: in the app's country list the recommended one is marked, and in your account → "Connection" → "Manual" every server shows its load percentage. From Russia, servers in Belarus, Kazakhstan and Germany are often faster than the Netherlands — try two or three.

3. 3

   Check the Wi-Fi, not the VPN

   Weak Wi-Fi caps the speed before the tunnel does. Measure the speed without the VPN right next to the router and in a far room: a big difference means the network is the problem. Connect the computer with a cable, switch the phone to the 5 GHz band, and move the router away from walls and the microwave.

4. 4

   Check MTU and DNS

   Speed test looks normal, but sites "hang"? That is not a slow channel — it is MTU or DNS. The NvoVPN app picks the packet size itself; in a manual configuration, add MTU = 1420 — exactly how is in the section below. A site "thinks" for a long time and then opens fast — that is DNS: reconnect and change the server.

MTU in WireGuard and AmneziaWG: why heavy pages hang, and what value to set

MTU is the largest data packet a network passes through whole. A VPN adds its own header to every packet, making it bigger. If the network will not pass packets that size and does not report it, large packets simply get lost. The sign: messenger messages go through, but heavy pages and downloads stall halfway.

The NvoVPN app picks the size itself — there is nothing to touch. In a manual configuration — on a router, in Linux, or in a third-party client — open the .conf file and add a line to the [Interface] section:

[Interface]
MTU = 1420

Did not help? Set it to 1380. This applies to both the AmneziaWG file and the WireGuard variant from your account: it is the same protocol, with the same header. This kind of tuning is called WireGuard MTU tuning — nothing more complicated than one line in a file.

Other reasons a VPN slows down: stealth mode, the carrier, a second tunnel, antivirus

• Stealth mode instead of AmneziaWG. If the app shows "Connected in disguise mode", the main protocol is throttled on this network, and traffic goes through VLESS stealth mode. It is more resilient but slower, especially on congested mobile networks. This is not a malfunction — that is how protection against blocking works. Switch to Wi-Fi, where the main protocol usually gets through, or try another server: sometimes only one specific route is filtered.
• The carrier is throttling the VPN. Some carriers strangle recognized VPN traffic, or all UDP: the connection exists, but speed is several times lower than without the VPN, and changing the server does not help. The sign: fast on home Wi-Fi, slow on mobile data. Stealth mode helps: it travels over TCP, like ordinary HTTPS. Turn on "Maximum reliability" on the app's home screen — or switch networks.
• Slow DNS and a second tunnel. On Android, switch "Private DNS" to "Automatic"; on iPhone and Mac, turn off iCloud "Private Relay". Check that a second VPN, an antivirus's "secure DNS", or a browser's VPN mode is not running alongside — two tunnels nested inside each other cut speed in half.
• Antivirus and firewall. Some security software on Windows inspects every packet and noticeably slows down the VPN adapter. Add NvoVPN to the exceptions, or turn off protection for a minute: if speed goes up, you have found the cause.
• An old app version. Updates bring new servers and protocol optimizations. On a phone, update through the store; on a computer, download the installer from the apps page and install it over the old one — your sign-in stays.

What counts as normal

• A 5–10% drop from the no-VPN speed and +1–5 ms of latency is normal for AmneziaWG.
• Stealth mode is slower; by how much depends on the network that made it necessary.
• Speed "wanders" over the course of the day: in the evening, carrier links and servers are busier. Changing the server helps most often.
• A few megabits are enough for HD video, about 25 for 4K; for calls, stable latency matters more than megabits.

FAQ

Which protocol is the fastest? In NvoVPN, AmneziaWG: it matches WireGuard in speed. Stealth mode is the fallback for filtered networks. What sets them apart is in "AmneziaWG vs WireGuard: what is the difference".

Does changing the server help against carrier throttling? Usually not — the carrier throttles the protocol, not the address. Stealth mode or a different network helps.

Can a VPN be faster than no VPN? Sometimes, yes: if the carrier slows down specific sites or video and cannot recognize them inside the tunnel.

What MTU value should I set? Start with 1420; if heavy pages still hang, try 1380. The MTU = … line goes in the [Interface] section of the configuration file; there is nothing to configure in the NvoVPN app.

What should I tell support if nothing helped? Speed test results without and with the VPN against the same server, the server you chose, the network type (Wi-Fi or carrier), and the time of the test. With this data we can see a problem on our end and give a specific answer: contact support.

Related guides: What to do if the VPN will not connect · Why VPNs stop working and how stealth mode works · AmneziaWG vs WireGuard: what is the difference