first post; first contribution
Used for the first written submission or post on a blog, social media, forum, etc.
ブログの初投稿を書くのに緊張した。
I was nervous writing my first blog post.
彼の初投稿は多くの「いいね」をもらった。
His first post got many likes.
Compound of 初 (hatsu, 'first') and 投稿 (tōkō, 'post, contribution').