Common causes of congenital stridor in child -
STRIDOR

Due to upper airway obstruction,

Types -

Inspiratory stridor - Obstruction above vocal cords (supraglottic).
Expiratory stridor - Obstriction distal trachea.
Biphasic - From supragiottic or proximal tracheal.

Causes  Infective:

Croup (lanyngo tracheo bronchitis)
Bacterial trachetis
Retropharyngeal abscess

Congenital:

Laryngomalacia: 60% of all total most common cause.
Vocal cord paralysis - 2nd most common.
Subglottic stenosis - 3rd most common.  

Iatrogenic :

Long-term intubation leads to subglottic stenosis - the most common causes of Acquired stridor in children.
Neoplasm: Recurrent respiratory papilloma (RRP) MC a benign tumour and larynx.
Laryngeal web
Laryngomalacia
Haemangioma
Subglottic stenosis