will someone know if i watched their live video on instagram after it has ended
No, if you watched someone's live video on Instagram after it has ended, the person who hosted the live video will not receive any notification or information that you watched their live video.
However, if you commented, liked, or engaged with the live video during the broadcast, the person who hosted the live video may see your username in their engagement metrics after the live video has ended.
They will not know specifically that you watched the live video after it ended, but they will know that you engaged with their content during the live broadcast.
