Background: Stunting, a form of chronic malnutrition characterised by impaired growth and development, remains a significant public health issue with long-term consequences for cognitive capacity, productivity, and health. Adolescents' knowledge and awareness of nutrition, reproductive health, and healthy lifestyle practices play a crucial role in breaking the intergenerational cycle of stunting. In the digital era, web-based educational tools present an innovative opportunity to engage adolescents in health promotion.

Method: Using one treatment group to see true effectiveness in improving adolescent knowledge and perception in private junior high schools in Tasikmalaya City (Pre-Examination Pre-Post Design). The sample was adolescents aged 12-14 years. The sample number of 70 students.

Results: The average knowledge before using Sejati was 44.59 and increased to 53.99 with a ῥ value of 0.000 and a Spearman's ρ value of 0.741, which means that Sejati is effective in increasing students' knowledge about stunting. The results of the attitude assessment found that SEJATI was not effective in increasing adolescents' perception of early marriage, namely with a ῥ>α.

Discussion: Knowledge is closely related to exposure to information. The experience of getting information visually can be, and the use of gadgets as a medium makes knowledge transfer easier and more interesting and strengthens the message conveyed. Knowledge changes faster because the brain's cognitive processes do not use the ability to analyse to combine values and tastes, in contrast to perception, which is influenced by the value that a person has and the influence of the environment; this causes the effect on perception to be slower and requires a more complex process than just understanding information.

Conclusion: Web-based media and applications can be a positive thing in conveying information to teenagers in Indonesia, by combining audio and visuals that can be accessed through gadgets to make information easier to obtain.

Bayu Irianti has been a lecturer at the Diploma III Midwifery Study Program of the Ministry of Health of Poltekkes Tasikmalaya since 2019. She is actively conducting teaching, research, and community service in the field of obstetrics and reproductive health for women and adolescents. Graduated with a Master of Midwifery from Padjadjaran University in 2014. She actively writes a midwifery textbook. Her focused research on children and labour. Some of the research has been published in the Nasional Journal in Indonesia.