Captions: up to 4,000 characters
TikTok captions can be up to 4,000 characters long, including hashtags and mentions. Only the first line or two show under the video before the "more" button, so put the hook and the most important keywords first.
Bio, name and username
Your bio is limited to 80 characters, your display name to 30 and your username to 24. Usernames can only use letters, numbers, underscores and periods. Emojis and fancy fonts may count as more than one character.
Comments: 150 characters
Comments are limited to 150 characters. Replies follow the same limit, so keep answers short or reply with a video instead.
How many hashtags to use
There's no fixed hashtag limit other than the caption length, but three to five relevant hashtags usually work better than a long list. Mix one broad tag with specific ones that describe the video, because TikTok uses captions and hashtags for search.