Indonesia's mobile market runs on several national networks, with Telkomsel, Indosat Ooredoo Hutchison (IOH) and XL Axiata as the three with the broadest infrastructure. Telkomsel has the widest reach across Java, Bali, Lombok, Sumatra and Sulawesi, including many secondary towns and ferry ports where the other two can be thinner; IOH and XL compete closely in Jakarta, Surabaya, Denpasar and other major cities. All three report high population-level 4G coverage on the main tourist islands and have been extending 5G through Jakarta, Surabaya and Bali's southern resort strip, though remote Gili coves, Komodo sailing routes and highland villages in Flores or Sulawesi can still see thinner signal regardless of provider.

The Bali–Java–Lombok loop is Indonesia's most common tourist connectivity pattern. A traveller landing at Denpasar, moving overland to Ubud and the Gilis, then flying to Yogyakarta or Jakarta, stays on the same national networks throughout — domestic Indonesian territory, not separate roaming zones. Buying a local Telkomsel or XL tourist SIM at each airport is unnecessary for data continuity, though each local purchase still triggers Indonesia's identity-registration requirements and, for phones used long-term with a local SIM, the separate IMEI registration regime administered by the Ministry of Trade.

Indonesia requires identity registration for locally issued prepaid SIMs — a passport at the point of sale — and maintains an IMEI registration system for phones used with Indonesian SIMs beyond a short tourist window. A global data-only travel eSIM operates as a roaming service rather than a newly issued Indonesian line, so it sidesteps the local SIM registration step and does not trigger the IMEI clock the way inserting a physical Indonesian SIM can for longer stays.

The practical sequence: install the eSIM profile over Wi-Fi before the inbound flight, keep the home SIM active for calls and passcodes, switch on the data eSIM once landed — whether that is Denpasar, Jakarta or Lombok — and leave the same balance active through inter-island flights and fast-boat hops rather than rebuying at each port.

An Indonesian prepaid SIM from Telkomsel, IOH or XL requires passport-based identity registration at the point of sale, and long-term use with a local SIM can trigger Indonesia's IMEI registration requirements. A data-only travel eSIM skips the registration step and covers Bali, Java and Lombok on the same balance without rebuying at each island.