Internet and wi-fi are widely available throughout Vietnam. Something like 98% of hotels and guesthouses have wi-fi; only in very remote places (such as national parks) is it not standard. Wi-fi is almost always free of charge. Many cafes and restaurants also have (free) wi-fi. Connection speeds are normally good. Internet cafes are also available, costing 3000d to 8000d per hour.
Most travellers also surf the net using 3G or 4G mobile phone connections.