Autocomplete field search start character limitation? How can I limit the number of characters on when the search starts send a request to the server?

What happens if I do for example always call my own API (in the sense of using the autocomplete_path attribute)? Is the minimum still 3 characters?
Will you explain the search that you are using (ex.solr, default).
Basic limitation of characters is 3. if you want to increase this go to admin/config/search/settings and change the length of Minimum word length to index to your-limit and re-index the site. If you type minimum word length then only your search send a request to server.