For the Class 9 half-yearly exam, the syllabus varies by board and subjects. Generally, it covers approximately 50–60% of the academic year syllabus, focusing on foundational topics. You should check your specific board or school website to view the exact chapters for:

Mathematics

Science

Social Science

English & Language subjects

Hello Anjali, in the question you have not specified which curriculum you follow, also syllabus is not released like that, as yearly exam is under school , it's up to your school how much they wish to ask . Still assuming you follow CBSE I am sharing you a link which might be helpful.
https://cbseacademic.nic.in/curriculum_2025.html
(https://www.jagranjosh.com/articles/cbse-class-9-maths-syllabus-2024-2025-pdf-1712563731-1) (https://www.vedantu.com/syllabus/cbse-class-9-syllabus)