There are many users who don’t know istg meaning on Snapchat. Well ISTG stands for “I swear to god” and it is used to emphasize the truth. Below are some examples to use ISTG in different contexts:-
1. ISTG, I just saw Robert Downey Jr. on the subway.
2. ISTG, I am surely going to leave you alone if you don’t come on time tomorrow.
3. From tomorrow onwards, I’ll be there on time, ISTG.
ISTG means "i swear to God" and is used at the time when they want people to trust them at any cost.