Wi-fi accessibility in hotels, cafes, restaurants and bars is generally good. The best option is to bring a wi-fi equipped smartphone, tablet or laptop or purchase a local SIM card on arrival. Chain restaurants and cafes with free wi-fi sometimes still require a Chinese phone number to receive a login code.
The Chinese authorities maintain strong controls on internet access. Around 10% of websites are blocked; the list is constantly changing but includes sites and apps such as Facebook, Twitter, Instagram, Google-owned sites (YouTube, Google Maps, Gmail, Google Drive), Whatsapp, Dropbox and many international media outlets, so plan ahead.
Many users have gained access to blocked websites by using a VPN (Virtual Private Network) service such as VyprVPN (www.goldenfrog.com). However, China's cyber security laws are changing rapidly, including controls on the use of VPNs, so check the Ministry of Industry and Information Technology's website (www.miit.gov.cn, Mandarin only) to ensure you are adhering to local laws. A VPN must be installed on devices before departing for China.