Bali's connectivity has improved a lot in the last few years. Seminyak, Kuta, Canggu, and Ubud all have solid 4G. You won't struggle with your internet connection in any of the main tourist areas.
The smaller islands are where it gets interesting.
Coverage by area
Seminyak, Kuta, Legian: Dense coverage. Multiple bars of 4G everywhere in the main strips, beach clubs, and hotel areas.
Canggu: Excellent. The digital nomad scene here has made reliable internet almost a local amenity - coworking spaces, cafes, and accommodation all have fast WiFi, and 4G backs it up outside.
Ubud: Good in town and the main tourist sites (Tegallalang rice terraces, Sacred Monkey Forest, Tirta Empul). Drops off in remote rice paddy areas and jungle valley walks. The Campuhan Ridge Walk has decent signal throughout, oddly.
Nusa Lembongan and Nusa Ceningan: Solid 4G now in the main areas. Much better than a few years ago.
Nusa Penida: Coverage has improved significantly. Kelingking Beach, Angel's Billabong, and the main port area (Toyapakeh) are fine. East coast and some interior areas can be patchy. Download offline maps before you take the fast boat from Sanur.
Amed and the northeast coast: Decent in town, variable on the dive sites. USAT Liberty wreck at Tulamben has reasonable signal on the beach.
Local SIM vs eSIM in Bali
Telkomsel's Kartu As Tourist SIM is available at Ngurah Rai Airport for around 150,000-200,000 IDR (about 8-10 pounds) with 15-30GB for 30 days. Cheap. Works well. The counter is clearly signposted at arrivals.
eSIM beats local SIM here if: you're arriving late at night when kiosks may be closed, you want to be connected from the moment you land, or Bali is part of a multi-country Southeast Asia trip covered by a regional plan.
How much data?
For a two-week Bali trip with moderate use - Maps, WhatsApp, Instagram stories, no streaming: 4-5GB. If you're posting a lot of content or doing video calls from beachside cafes, 8-10GB. The digital nomads in Canggu running businesses off mobile hotspots aside, most holiday travellers find 5GB very comfortable for two weeks.
Getting around Bali with data
Grab is the ride-hailing app you'll use most in Bali. It works like Uber and needs a data connection to book rides. Prices are reasonable - a 30-minute ride from Seminyak to Ubud costs around 150,000-200,000 IDR (roughly $10-13). The app also shows food delivery options, which is handy if you're staying in a villa and don't feel like going out.
Google Maps is mostly accurate for Bali, but some of the smaller alleyways (gangs) in Ubud and Seminyak can be tricky. Locals often give directions by landmarks rather than street names. "Past the big banyan tree, turn left at the temple" is a real direction you'll get. Having Maps running helps you confirm you're on the right track.
Scooter rental and data
Most tourists rent scooters in Bali. If you're doing that, having mobile data for navigation is almost essential. The roads between towns aren't always well-signed, and taking a wrong turn on a narrow mountain road with no cell service isn't ideal. Mount your phone on the scooter handlebars (cheap phone holders are sold everywhere) and use Google Maps with voice navigation. Just keep the screen brightness up - Bali's sun makes screens hard to read.
Rainy season and connectivity
Bali's wet season runs roughly November through March. Heavy tropical rain can temporarily degrade cell signal, though it usually bounces back within minutes. The bigger issue is that you'll spend more time indoors, which means more data usage for entertainment. If you're visiting during wet season, bump your data estimate up by a couple of GB.
Temple visits and offline prep
Bali has thousands of temples, and the major ones (Tanah Lot, Uluwatu, Besakih, Tirta Empul) all have good cell coverage. But if you're exploring smaller, less-touristed temples in the inland villages, signal can be unpredictable. Before heading to any temple, download the location pin and check the dress code requirements online - most temples require a sarong and sash, and some visitors get turned away. Having this info on your phone saves the embarrassment.
Uluwatu Temple is worth a special mention: the Kecak fire dance performance at sunset is stunning, and you'll want data to book tickets or check the schedule. The clifftop temple area has decent 4G, so posting that sunset photo in real time is very doable.
Cafes and coworking with data
Bali's cafe culture is a big part of the experience. Most cafes in Canggu and Ubud have WiFi, but the passwords change regularly and the speeds can be terrible during peak hours. Having eSIM data as backup means you're not stuck refreshing a page for 3 minutes while the barista deals with a line of customers before giving you the new WiFi password. First-world problems, sure, but if you're trying to book tomorrow's tour or check ferry schedules to Nusa Penida, waiting around for WiFi is annoying.
Best plan for Bali
Telkomsel-based eSIM plans have the best Bali coverage. If you're island-hopping through Indonesia (Bali, Lombok, Komodo, Java), grab a plan that covers the whole country rather than just Bali. Check getesimonline.com for Indonesia options at /esim-in-indonesia.