Most high chair manufacturers don’t recommend using their products before 6 months. However, the most important consideration when it comes to deciding when to introduce Baby to their high chair is not how many months old they are, but if they are able to sit up and support their head on their own.
This milestone does often happen around the 6-month mark, it’s true, but if Baby is sitting up on their own and holding their head up pretty steadily at 4 or 5 months, there’s no harm in speeding up that timeline a little. If, on the other hand, Baby is still feeling out this whole ‘sitting’ thing at 7 months, don’t rush them – just wait a little longer on the high chair.
If Baby’s developmental timeline lines up in a convenient way, it can be a good idea to introduce Baby to the high chair a little bit before introducing solid food, so that they are already used to the high chair by the time solid-food-time comes around.