⚡ Quick Verdict:
- Chạy: Surfshark starts at $1.99/mo (2-year plan) vs AdGuard VPN at $2.40/mo (2-year plan)
- Phù hợp nhất cho: Surfshark for streaming and unlimited devices, AdGuard VPN for ad blocking and light browsing
- Điểm khác biệt chính: Surfshark offers unlimited simultaneous connections and 3,200+ servers; AdGuard VPN caps at 10 devices with 800+ servers
- Our pick: Surfshark for most users — faster speeds, larger server network, and better streaming support
Surfshark and AdGuard VPN target very different types of VPN users.
One gives you unlimited device connections and a massive server network.
The other bundles ad blocking with basic VPN protection.
This comparison breaks down both tools so you can pick the right fit.
If you want a full Surfshark review or AdGuard VPN review, check our detailed breakdowns linked below.
Toàn cảnh
This SurfsharkVPN vs AdGuard VPN comparison covers pricing, features, and ease of use.
We also break down who each VPN service works best for.
Our sources include published specs, documentation, and user reviews.
By the end, you’ll know which VPN provider fits your needs.
Surfshark là gì?
Surfshark is a VPN service that protects your internet connection.
It hides your real IP address and encrypts all your web traffic.
Ứng dụng Surfshark hoạt động trên hệ điều hành Windows. Máy MaciOS, Android và Linux.
It stands out by offering unlimited simultaneous connections on one plan.
Surfshark’s servers run on the OpenVPN protocol and WireGuard for fast speeds.
Cá mập lướt sóng
Surfshark VPN gives you unlimited device connections and 3,200+ servers in 100 countries. It uses AES-256 encryption and has a Deloitte-audited no-logs policy.
Bảng giá Surfshark
Here’s what a Surfshark subscription costs in 2026.
| Kế hoạch | Giá | Tốt nhất cho |
|---|---|---|
| 24 tháng + 3 tháng bổ sung | 1,99 đô la/tháng | Giá trị tốt nhất cho người dùng lâu dài |
| 12 tháng + 3 tháng bổ sung | 3,19 đô la/tháng | Cam kết trung hạn kèm theo tiết kiệm |
| 1 tháng | 15,45 đô la/tháng | Ngắn hạn hoặc để thử nghiệm dịch vụ |
Pricing verified May 2026.
Dùng thử miễn phí: Yes — 7-day free trial on Android and iOS devices. No credit card needed to start.
Đảm bảo hoàn tiền: 30-day money-back guarantee on all plans. Contact support within 30 days for a full refund.
📌 Ghi chú: Sinh viên được giảm thêm 15% khi đăng ký qua Học sinh Beans. The 2-year plan includes 3 bonus months, so you pay for 24 and get 27 months total.
⚠️ Cảnh báo: Surfshark pricing increases after the first billing cycle. Renewal rates are higher than the introductory price, and 2-year plans cannot be renewed at the same rate.
Những lợi ích chính của Surfshark
Here’s what makes Surfshark worth considering:
- Không giới hạn thiết bị: Connect every device in your household on one plan. No caps on simultaneous connections.
- Mạng máy chủ quy mô lớn: Over 3,200 VPN servers across 100 countries. That gives you plenty of server locations to choose from.
- Trình chặn quảng cáo CleanWeb: Blocks ads, trackers, and malware at the VPN level. No extra browser extensions needed.
- Kết nối đa bước: Route your network traffic through two VPN servers for extra privacy. Dynamic MultiHop lets you pick custom server pairings.
- Mã định danh thay thế: Create a fake online identity for signups. Protects your real IP address and personal info.
- Bảo mật được kiểm toán: Deloitte and Cure53 have verified Surfshark’s no-logs policy. Your browsing history stays private.
- Tốc độ nhanh: All Surfshark servers run at 10 Gbps. The WireGuard protocol keeps download speeds high. Speed tests from review sites confirm strong upload speed as well.
- Tùy chọn IP chuyên dụng: You can add a dedicated IP address in 20 locations. Surfshark also offers a virtual phone number and an IP rotator feature that rotates your virtual IP address automatically.
- Hỗ trợ nền tảng rộng rãi: Surfshark’s Windows app, mobile apps, and browser extensions cover all your devices. It also works on Apple TV and Android TV for streaming on big screens.
What Our Team Noticed
Của chúng tôi nhà văn signed up for Surfshark and spent several days exploring the platform. Here’s what stood out:
Ưu điểm và nhược điểm của Surfshark
✅ Ưu điểm
- Số lượng kết nối đồng thời không giới hạn trên tất cả các gói cước.
- Hơn 3.200 máy chủ tại 100 quốc gia với tốc độ nhanh.
- Chính sách không lưu nhật ký được kiểm toán độc lập bởi Deloitte.
- Tích hợp trình chặn quảng cáo, phân luồng dữ liệu và công tắc ngắt khẩn cấp.
- Works well with Netflix, Hulu, and Disney+ for streaming
❌ Nhược điểm
- Giá gia hạn cao hơn nhiều so với giá khuyến mãi ban đầu.
- Based in Netherlands (part of Nine Eyes alliance)
- Một số máy chủ có thời gian kết nối không ổn định.
- Monthly plan at $15.45 is expensive for short-term use
Ad Guard VPN là gì?
AdGuard VPN is a privacy-focused VPN service from AdGuard Software Limited.
It encrypts your internet traffic and hides your real location.
The AdGuard VPN app works on Windows, macOS, Android, iOS, and Linux.
It pairs well with the AdGuard ad blocker for DNS-level ad blocking.
The VPN is especially useful on public wi fi networks where your data is at risk.
VPN AdGuard
AdGuard VPN uses a proprietary protocol and AES-256 encryption. It includes a free plan with 3 GB/month and supports up to 10 simultaneous connections on paid plans.
Bảng giá VPN AdGuard
Here’s what an AdGuard VPN subscription costs in 2026.
| Kế hoạch | Giá | Tốt nhất cho |
|---|---|---|
| 1 tháng | 11,99 đô la/tháng | Short-term or testing the VPN service |
| 1 năm | 3,99 đô la/tháng | Cam kết hàng năm kèm theo tiết kiệm |
| 2 năm | 2,40 đô la/tháng | Giá trị tốt nhất cho người dùng lâu dài |
Pricing verified May 2026.
Dùng thử miễn phí: AdGuard VPN offers a free plan with 3 GB of data per month. No credit card needed.
Đảm bảo hoàn tiền: 30-day money-back guarantee on yearly and bi-annual plans.
📌 Ghi chú: AdGuard VPN accepts credit cards, PayPal, and tiền điện tử payments. The free version caps speeds at 20 Mbps and limits you to a few server locations.
⚠️ Cảnh báo: AdGuard VPN has not undergone any third-party audits to verify its no-logs claims. This is a gap compared to audited VPN providers like Surfshark.
Những lợi ích chính của AdGuard VPN
Here’s what makes AdGuard VPN worth considering:
- DNS-Level Ad Blocking: Block ads and trackers through custom DNS servers. Works at the system level, not just in browsers.
- Gói miễn phí có sẵn: Get 3 GB of data every month at no cost. Good for light browsing and testing.
- Thẩm quyền pháp lý của Síp: Based outside the 5/9/14 Eyes alliances. Also complies with GDPR rules.
- Giao thức độc quyền: AdGuard VPN’s protocol masks VPN traffic as regular HTTPS traffic. Helps avoid VPN detection in some regions.
- Hiện tượng phân tách đường hầm: Choose which apps or websites go through the VPN tunnel. Route the rest through your normal internet connection.
- Hỗ trợ đa nền tảng: Apps for Windows, macOS, Android, iOS, Android TV, and browser extensions for Chrome, Firefox, and Edge. AdGuard VPN’s apps are easy to use apps with a clean interface for mobile devices and desktop apps.
What Our Team Noticed
Our writer signed up for AdGuard VPN and spent several days exploring the platform. Here’s what stood out:
Ưu điểm và nhược điểm của AdGuard VPN
✅ Ưu điểm
- Free plan with 3 GB monthly data for light use
- DNS-level ad and tracker blocking built in
- Based in Cyprus, outside the 14 Eyes surveillance alliances
- Giao thức độc quyền ngụy trang lưu lượng VPN thành HTTPS.
❌ Nhược điểm
- Only 800+ servers in 65 locations — much smaller network
- Không có cuộc kiểm toán an ninh của bên thứ ba nào để xác minh các tuyên bố này.
- Limited to 10 simultaneous connections on paid plans
- No 24/7 customer support — relies on a ticketing system
- Tốc độ có thể giảm đáng kể trên các máy chủ ở xa.
So sánh tính năng
Let’s compare Surfshark and AdGuard VPN across 10 key features. This will help you decide which VPN provider matches your needs.
| Tính năng | Cá mập lướt sóng | VPN AdGuard |
|---|---|---|
| Giá khởi điểm | 1,99 đô la/tháng | 2,40 đô la/tháng |
| Gói miễn phí | ❌ (Dùng thử 7 ngày) | ✅ (3 GB/tháng) |
| Mạng máy chủ | Hơn 3.200 sản phẩm tại 100 quốc gia | Hơn 800 sản phẩm tại 65 địa điểm |
| Kết nối thiết bị | Không giới hạn | Tối đa 10 |
| Name | ✅ | ✅ |
| Chia đường hầm | ✅ | ✅ |
| Bộ chặn quảng cáo | ✅ (CleanWeb) | ✅ (DNS-level) |
| Kiểm toán độc lập | ✅ (Deloitte, Cure53) | ❌ |
| Hỗ trợ phát trực tuyến | Netflix, Hulu, Disney+ | Netflix, Disney+ (limited) |
| Tốt nhất cho | Families, streaming, privacy | Ad blocking, light browsing |
1. Mạng lưới và vị trí máy chủ
Surfshark: Surfshark runs 3,200+ servers across 100 countries. All servers have been upgraded to 10 Gbps throughput. The large network means less crowding and more server locations to pick from.
VPN AdGuard: AdGuard VPN operates around 800 servers in 65+ locations across 53 countries. The network is much smaller, which can mean slower speeds during peak hours and fewer options for bypassing geo-restrictions.
2. Mã hóa & Giao thức VPN
Surfshark: Surfshark uses AES-256 encryption with the WireGuard protocol by default. It also supports OpenVPN and IKEv2. WireGuard is known for fast download speeds and strong security. All data is Surfshark encrypted before leaving your device, keeping you safe on public wi fi.
VPN AdGuard: AdGuard VPN also uses AES-256 encryption but relies on its own proprietary protocol. This protocol masks VPN traffic as HTTPS, which can help avoid detection. However, it has not been independently audited, which raises transparency concerns.
⚠️ Cảnh báo: AdGuard VPN does not support WireGuard or OpenVPN. If you need a widely tested, open-source VPN protocol, Surfshark is the safer pick.
3. Device Connections
Surfshark: Surfshark offers unlimited simultaneous connections on every plan. One subscription covers all your devices — phones, tablets, laptops, smart TVs, and routers. This makes it ideal for families.
VPN AdGuard: Paid plans allow up to 10 simultaneous connections. The free version is limited to just 2 devices. For a household with many devices, this cap can be frustrating.
4. Ad & Malware Blocking
Surfshark: CleanWeb blocks ads, trackers, and malware at the VPN level. It works across all apps, not just your browser. You can also block cookie pop-ups automatically.
VPN AdGuard: Ad blocking is where AdGuard shines. The AdGuard DNS server blocks ads and trackers at the DNS level. When paired with the AdGuard ad blocker app, you get deep system-wide ad blocking on mobile devices.
5. Chính sách bảo mật và không lưu nhật ký
Surfshark: Surfshark’s no-logs policy has been independently audited by both Deloitte and Cure53. The company does not log browsing history, session info, or network traffic. IP addresses are kept for a maximum of 15 minutes after a session ends.
VPN AdGuard: AdGuard VPN has a strict no-logs policy and does not record IP addresses, browsing history, or connection timestamps. However, this has not been verified by any third-party audit. AdGuard is based in Cyprus, which complies with GDPR.
6. Tốc độ & Hiệu suất
Surfshark: Surfshark delivers fast download speeds, especially on the WireGuard protocol. All servers run at 10 Gbps capacity. Speed tests from multiple review sites confirm strong performance on both nearby and distant servers.
VPN AdGuard: AdGuard VPN’s performance is generally below average compared to other VPN services. Paid plans can reach around 58 Mbps average. The free version caps speeds at 20 Mbps, which limits streaming and data-intensive tasks.
7. Phát trực tuyến & Bỏ chặn
Surfshark: Surfshark can unblock Netflix, Hulu, Disney+, and other streaming platforms without issues. Users report buffer-free streaming experiences. The large server network helps find working servers quickly.
VPN AdGuard: AdGuard VPN can unblock Netflix, Disney+, and BBC iPlayer. However, it struggles with Amazon Prime and Peacock. Streaming performance varies, and some users report buffering on certain platforms.
8. Hiện tượng phân nhánh đường hầm
Surfshark: The split tunneling feature (called Bypasser) lets you route certain websites and apps outside the VPN tunnel. This keeps your banking apps on your real IP address while everything else goes through the VPN.
VPN AdGuard: AdGuard VPN also supports split tunneling. You can choose which apps or certain websites bypass the VPN connection. The feature works on both desktop apps and mobile devices.
9. Hỗ trợ khách hàng
Surfshark: Surfshark offers 24/7 live chat support along with email support and a knowledge base. Response times are fast, and the support team handles VPN configuration and connection issues quickly.
VPN AdGuard: AdGuard VPN does not have 24/7 live chat. The support team works through a ticketing system and email. Response times can take longer compared to VPN providers with round-the-clock chat.
10. Định giá & Chi phí
Hãy cùng so sánh các gói giá cạnh nhau.
| Kế hoạch | Cá mập lướt sóng | VPN AdGuard |
|---|---|---|
| Miễn phí | ❌ (Chỉ dùng thử 7 ngày) | ✅ (3 GB/tháng) |
| Hàng tháng | 15,45 đô la/tháng | 11,99 đô la/tháng |
| 1 năm | 3,19 đô la/tháng | 3,99 đô la/tháng |
| 2 năm | 1,99 đô la/tháng | 2,40 đô la/tháng |
Surfshark: The 2-year plan at $1.99/month is cheaper than AdGuard VPN’s equivalent. You also get unlimited devices, a larger server network, and faster speeds. The monthly plan at $15.45 is expensive, though.
VPN AdGuard: The monthly plan at $11.99 is cheaper than Surfshark’s $15.45 monthly rate. AdGuard also offers a free plan. But the 2-year rate is $0.41 more per month than Surfshark, with fewer features included.
Các kịch bản khác nhau
| Nếu bạn cần… | Chọn | Tại sao |
|---|---|---|
| Ngân sách eo hẹp (dài hạn) | Cá mập lướt sóng | $1.99/mo vs $2.40/mo on 2-year plans |
| Free VPN for light use | VPN AdGuard | 3 GB free plan available |
| Kết nối thiết bị không giới hạn | Cá mập lướt sóng | Không giới hạn số lượng thiết bị so với 10 thiết bị khác. |
| Best ad and tracker blocking | VPN AdGuard | DNS-level blocking with AdGuard tools |
| Xem Netflix và Disney+ trực tuyến | Cá mập lướt sóng | Better unblocking and faster speeds |
| Bảo mật không lưu nhật ký đã được xác minh | Cá mập lướt sóng | Deloitte + Cure53 audits |
💰 Ngân sách của bạn
Surfshark is cheaper on 2-year plans at $1.99/month. AdGuard VPN is cheaper month-to-month at $11.99 and also offers a free plan for light browsing.
🔌 Bộ công nghệ của bạn
Surfshark has browser extensions for Chrome, Firefox, and Edge. AdGuard VPN works well with the AdGuard ad blocker and AdGuard DNS for deep system-wide ad blocking on Android.
📺 Nhu cầu xem trực tuyến của bạn
Surfshark unblocks more streaming platforms and delivers faster speeds. AdGuard VPN can handle Netflix and Disney+ but struggles with Amazon Prime and Peacock.
🎓 Trình độ kinh nghiệm của bạn
Both VPN services are easy to use with simple apps. Surfshark’s app has more features but is still beginner-friendly. AdGuard VPN is more bare-bones, which some users prefer.
🆓 Dùng thử và bản demo miễn phí
Surfshark offers a 7-day free trial on mobile with a 30-day money-back guarantee. AdGuard VPN gives you a free plan with 3 GB/month — no credit card required.
🛟 Các tùy chọn hỗ trợ
Surfshark has 24/7 live chat and email support. AdGuard VPN relies on a ticketing system without live chat, so response times may be slower.
Hướng dẫn chuyển đổi
Bạn đã sử dụng một trong những công cụ này rồi? Dưới đây là những điều bạn cần biết nếu chuyển sang sử dụng công cụ khác.
🔄 Bạn đang chuyển từ Surfshark sang AdGuard VPN?
✅ Những lợi ích bạn sẽ nhận được:
- Free plan with 3 GB/month — no payment needed
- DNS-level ad blocking that pairs with AdGuard products
- Cyprus jurisdiction outside the 14 Eyes alliances
❌ Những gì bạn sẽ mất:
- Unlimited device connections (capped at 10 on AdGuard VPN)
- 3,200+ server network drops to 800+ servers
- Chính sách không lưu nhật ký được kiểm toán độc lập
📋 Cách chuyển đổi:
- Hủy đăng ký Surfshark của bạn trước khi gia hạn
- Download the AdGuard VPN app on your devices
- Create an AdGuard account and pick a plan (or use the free version)
🔄 Bạn đang chuyển từ AdGuard VPN sang Surfshark?
✅ Những lợi ích bạn sẽ nhận được:
- Kết nối đồng thời không giới hạn cho tất cả các thiết bị của bạn.
- 3,200+ servers in 100 countries with 10 Gbps speeds
- WireGuard protocol and audited privacy policy
❌ Những gì bạn sẽ mất:
- Gói miễn phí với dung lượng dữ liệu hàng tháng.
- DNS-level ad blocking paired with AdGuard apps
- Cyprus-based jurisdiction outside all surveillance alliances
📋 Cách chuyển đổi:
- Cancel your AdGuard VPN subscription or let it expire
- Install Surfshark on your devices from surfshark.com
- Pick a plan and connect — Surfshark works on all your devices right away
What Our Review Didn’t Cover
This comparison focused on individual users and small households. We didn’t test enterprise VPN configurations, obfuscated servers, or how either VPN company handles data intensive tasks like video calls. We also didn’t evaluate Surfshark’s Windows app or its windows version for a Windows PC in depth, nor did we test the Android app on Android TV. Our observations are based on May 2026 versions — features and pricing may change. If you need a VPN for online gaming or advanced VPN configuration, your priorities may differ from what we’ve covered here.
Phán quyết cuối cùng
| Loại | Người thắng |
|---|---|
| 💰 Giá cả (Dài hạn) | Cá mập lướt sóng |
| Gói miễn phí 🆓 | VPN AdGuard |
| 🚀 Mạng máy chủ | Cá mập lướt sóng |
| ⚡ Tốc độ & Hiệu suất | Cá mập lướt sóng |
| 🛡️ Bảo mật & Kiểm toán | Cá mập lướt sóng |
| 🔌 Chặn quảng cáo | VPN AdGuard |
| 📺 Phát trực tuyến | Cá mập lướt sóng |
| 👶 Dễ sử dụng | Cà vạt |
| 🏆 Người chiến thắng chung cuộc | Cá mập lướt sóng |
🏆 NGƯỜI CHIẾN THẮNG: Surfshark
Surfshark wins 5 out of 8 categories.
Phù hợp nhất cho: Families with multiple devices, streaming fans, and privacy-focused users who want an audited VPN.
Surfshark and AdGuard VPN serve different audiences. Surfshark is a full-featured VPN with unlimited connections, fast speeds, and proven privacy through independent audits. AdGuard VPN is a lighter option that works best for users who want simple browsing protection with strong ad blocking.
AdGuard VPN wins on its free plan and DNS-level ad blocking. If you already use AdGuard products, the VPN fits naturally into that setup. But for most users who need a VPN for online privacy, streaming, or protecting multiple devices, Surfshark offers more features at a lower long-term price.
So sánh thêm về Surfshark
Here’s how Surfshark stacks up against other VPN providers:
Surfshark so với NordVPN
Surfshark thắng nhờ: Lower price ($1.99 vs $3.09/mo), unlimited device connections, and a more budget-friendly entry point for families
NordVPN thắng điểm ở các khía cạnh sau: Larger server network (5,000+ servers), faster raw speeds on many connections, and double the server count in key regions
Surfshark so với ExpressVPN
Surfshark thắng nhờ: Significantly cheaper pricing, unlimited device connections (ExpressVPN caps at 8-14), and CleanWeb ad blocker included
ExpressVPN thắng thế ở các điểm sau: Consistent speeds across distant servers, broader router support, and a longer track record with streaming platforms
So sánh Surfshark và Proton VPN
Surfshark thắng nhờ: More server locations (100 countries vs 68), unlimited devices, and lower 2-year pricing
Proton VPN thắng thế ở các điểm sau: A genuinely useful free plan with no data caps, open-source apps, and Swiss privacy jurisdiction
Surfshark vs CyberGhost
Surfshark thắng nhờ: Unlimited simultaneous connections, more compact and intuitive app design, and WireGuard as the default protocol
CyberGhost thắng nhờ: Dedicated streaming and torrent servers, larger total server count, and 45-day money-back guarantee on long plans
So sánh thêm về AdGuard VPN
Here’s how AdGuard VPN stacks up against other VPN providers:
AdGuard VPN so với NordVPN
AdGuard VPN thắng thế ở các điểm sau: Free plan with 3 GB data, lower monthly price ($11.99 vs $12.99), and built-in DNS-level ad blocking
NordVPN thắng điểm ở các khía cạnh sau: 5,000+ servers, independently audited privacy, 24/7 live support, and much faster connection speeds
AdGuard VPN vs Proton VPN
AdGuard VPN thắng thế ở các điểm sau: DNS-level ad blocking, integration with AdGuard ad blocker, and proprietary HTTPS-masking protocol
Proton VPN thắng thế ở các điểm sau: Free plan with no data cap, open-source audited apps, Secure Core servers, and Swiss jurisdiction
AdGuard VPN so với Private Internet Access
AdGuard VPN thắng thế ở các điểm sau: Free plan for light users, simpler app interface, and DNS-level ad blocking out of the box
Private Internet Access thắng thế ở các điểm sau: Larger server network, open-source client, unlimited device connections, and proven no-logs record in court
Câu hỏi thường gặp
VPN Surfshark có đáng tin cậy không?
Yes. Surfshark has been audited by Deloitte and Cure53, both confirming its no-logs policy. The VPN uses AES-256 encryption and the WireGuard protocol to protect your internet connection.
Ad Guard VPN có an toàn không?
AdGuard VPN uses AES-256 encryption and has a strict no-logs policy. However, it has not undergone any third-party security audits. The company is based in Cyprus and complies with GDPR.
Tôi có thể sử dụng Surfshark VPN miễn phí không?
Surfshark does not have a permanent free plan. It offers a 7-day free trial on iOS and Android devices. All plans come with a 30-day money-back guarantee.
Người bảo vệ Phó chủ tịch có kế hoạch miễn phí chứ?
Yes. The free version gives you 3 GB of data per month with access to a few server locations. Speeds are capped at 20 Mbps on the free plan.
Which is better for streaming, Surfshark or AdGuard VPN?
Surfshark is the better pick for streaming. It unblocks Netflix, Hulu, Disney+, and more. AdGuard VPN can handle Netflix and Disney+ but struggles with other platforms like Amazon Prime.
Gói đăng ký Surfshark có giá bao nhiêu?
Surfshark pricing starts at $1.99/month on the 2-year plan. The 1-year plan costs $3.19/month. A single month costs $15.45. Surfshark also accepts Google Pay and credit cards.
VPN AdGuard có chặn quảng cáo không?
Yes. AdGuard VPN can block ads through its DNS servers. When you use AdGuard VPN with the AdGuard ad blocker, you get system-wide blocking ads on mobile devices and desktop apps. The free version includes this feature too.
Is Surfshark a good VPN for online security?
Yes. Surfshark encrypts your traffic with AES-256 and offers standard VPN features like a kill switch, split tunneling feature, and IP rotator. It also provides a dedicated IP address option and a virtual phone number add-on for extra online privacy. Surfshark’s security measures include a strict no-logs policy verified by Deloitte.
Can I buy AdGuard VPN risk free?
Yes. AdGuard offers a 30-day money back guarantee on yearly and 2-year plans. You can also test the free version first to see if AdGuard VPN’s apps work for your needs. AdGuard VPN’s performance on a US server is decent for everyday browsing.
English 
Spanish 
Chinese 
German 
French 
Arabic 
Russian 
Portuguese 
Japanese 
Korean 
Italian 
Turkish 
Dutch 
Polish 
Indonesian 
Thai 
Vietnamese 