<p>Over-irrigation and under-irrigation can lead to reduced yields and increased input costs due to nutrient leaching, emphasizing the need for better irrigation management techniques. A two-year field experiment (2022 &amp;2023) was conducted at the Mhtsab Azmati irrigation scheme in Northern Ethiopia to explore the applicability of the Wetting Front Detector (WFD), a simple on-farm water optimization technology, by comparing it with the computer-based Crop water requirement (CROPWAT 8.0) and farmers’ irrigation practices (FIP) for onion production. A randomized complete block design (RCBD) was used for the field experiment, replicated four times, evaluating water savings, productivity, yields, water use efficiency, and economic water productivity. Results showed a significant difference (p &lt; 0.05) in water applied among CROPWAT 8.0, WFD, and FIP. CROPWAT 8.0 saved 36.55% of irrigation water, while WFD saved approximately 19.15% compared to FIP. Total and marketable yields using WFD (33.48 t ha⁻¹ and 32.6 t ha⁻¹) were not significantly different from CROPWAT 8.0 (35.73 t ha⁻¹ and 35.1 t ha⁻¹) but were higher than FIP (25.25 t ha⁻¹ and 23.9 t ha^−1). Unmarketable yields from WFD (0.875 t ha⁻¹) were comparable to CROPWAT 8.0 (0.625 t ha⁻¹) and FIP (1.354 t ha⁻¹). The mean water productivity for CROPWAT 8.0, WFD, and FIP was 5.633&#xa0;kg&#xa0;m⁻³, 4.17&#xa0;kg&#xa0;m⁻³, and 2.505&#xa0;kg&#xa0;m⁻³, respectively. The study concludes that both CROPWAT 8.0 and WFD significantly improved irrigation efficiency, yield, and water productivity compared to traditional FIP. Although CROPWAT 8.0 provided the highest water savings and productivity, its dependence on computer-based modeling may limit its practicality for smallholder farmers. Thus, the WFD offered a more accessible and user-friendly alternative with comparable yield outcomes. Therefore, the simpler tool WFD should be used to improve current on-farm water optimization, as it is easily applicable by smallholder irrigators.</p>