Our research aimed to quantify urban expansion implicated by the overtourism phenomenon in Canggu, Bali, a crucial issue for local and international citizens. Other researchers have not explored this area extensively, despite its recent popularity and complex environmental problems. However, our examination solely focuses on the expansion of built-up land in a time series spanning the past decade. To rapidly map urban growth, we processed archived Landsat imagery and computed the Index-Based Built-Up Index (IBI). We applied year-specific thresholds to classify each annual composite into built-up and non-built-up (vegetated/other) surfaces. Built-up expansion was then quantified for 2014–2024 and mapped at the village scale to show both extent and change. Built-up area increased by 317.97 ha (22.31%) over 2014–2024, with a sharp 177.84 ha (12.48%) rise concentrated in 2022–2024. Kerobokan Kelod (+2.95%), Tibubeneng (+2.14%), and Canggu (+1.85%) recorded the largest gains; Pererenan, Cemagi, and Beraban each added up to 0.82%. Over the same period, international tourist arrivals grew by an average of 71.22% per month, aligning with the acceleration of built-up expansion. We do not claim causality; however, the timing and spatial concentration near tourism corridors indicate strong tourism-related pressure on land conversion. Uncertainty arises from the IBI threshold used to separate built-up from non-built-up surfaces. Bare land can share spectral values with impervious surfaces and create mixed pixels. We binarized IBI using -0.10 in 2016 and 2020 and -0.08 in other years, so area estimates near these cutoffs are sensitive. A brief threshold-sensitivity test and validation with higher-resolution imagery will improve accuracy. Despite this limitation, the Landsat results show concentrated, tourism-linked built-up expansion around Canggu that coincides with the internationally publicized overtourism surge. These village-scale metrics provide clear evidence for local government to control land conversion, protect blue–green infrastructure, and refine spatial-planning regulations.