<![CDATA[Continuous monitoring of water quality plays an important role in supporting effective water resource management. This research develops a water quality monitoring system based on the Internet of Things (IoT) using an ESP8266 microcontroller integrated with a Total Dissolved Solids (TDS) sensor. The study includes hardware design, software development, system integration, and sensor accuracy evaluation by comparing the measurement results with a standard TDS meter. Testing was conducted on three water samples: bottled water, reverse osmosis (RO) gallon water, and tap water. The experimental results show measurement errors of 3.45%, 6.12%, and 6.67%, respectively. The average error obtained is 5.41%, indicating an overall system accuracy of 94.59%. In addition, the system is capable of measuring TDS values in real-time and transmitting the data to the server in a stable manner. These results indicate that the developed system is feasible for IoT-based water quality monitoring applications.Keywords: Internet of Things; Water Quality; ESP8266; TDS Sensor; Real-time Monitoring AbstrakPemantauan kualitas air secara berkelanjutan memiliki peran penting dalam mendukung pengelolaan sumber daya air yang efektif. Penelitian ini mengembangkan sistem monitoring kualitas air berbasis Internet of Things (IoT) dengan memanfaatkan mikrokontroler ESP8266 yang terintegrasi dengan sensor Total Dissolved Solids (TDS). Metode penelitian meliputi perancangan perangkat keras, pengembangan perangkat lunak, integrasi sistem, serta evaluasi akurasi sensor melalui perbandingan hasil pengukuran dengan alat ukur TDS meter. Pengujian dilakukan pada tiga sampel air, yaitu air kemasan, air galon reverse osmosis (RO), dan air keran. Hasil pengujian menunjukkan tingkat kesalahan sebesar 3,45%, 6,12%, dan 6,67%. Rata-rata kesalahan sistem sebesar 5,41% dengan tingkat akurasi mencapai 94,59%. Sistem juga mampu melakukan pengukuran nilai TDS secara real-time dan mengirimkan data ke server secara stabil. Dengan demikian, sistem yang dikembangkan layak digunakan untuk monitoring kualitas air berbasis IoT. ]]>
