Mobile Coverage in Sri Lanka: Visitors will likely find good mobile reception in cities and towns, though it may be spotty in rural areas.
International Roaming: Tourists can use their existing mobile service providers and switch to international roaming, but this can be expensive and not the best option for a long stay so ensure to have the roaming activated at least till the point you get the local SIM.
SIM Cards: Tourists can purchase a local SIM card upon arrival in Sri Lanka. Major carriers include Dialog, Mobitel, and Hutch, which offer various packages with affordable rates for data, voice calls, and SMS.
You can check further directly here as well:
https://www.mobitel.lk/prepaid/tourist-pack
https://www.dialog.lk/tourist-plans
https://www.airtel.lk/get-a-tourist-sim/
Wi-Fi: Wi-Fi is widely available in hotels, cafes, and restaurants in tourist areas, and many tourist destinations offer free Wi-Fi. However, don’t be surprised that there are areas still around where you will find no reception at all. So it’s advisable to always carry a combo SIM Pack like maybe a Dialog & SLT or Hutch & Mobitel so hopefully you have something working.
You can also check – https://soliswifi.co/pages/global-coverage for more options.
Portable Wi-Fi Devices: Portable Wi-Fi devices can also be rented or purchased, which provide Wi-Fi connectivity for multiple devices on the go.