In JSP, there are three types of comments, depending on what exactly you want:

📝 1. HTML Comments

<!-- This is an HTML comment -->

It will appear in the browser’s page source (users can see it if they view source).

Used to explain client-side code (HTML, CSS).

🛡️ 2. JSP Comments

<%-- This is a JSP comment --%>

It is completely removed during JSP translation (server-side).
Browser will never see this comment — it stays only on the server.
Used to hide server-side Java code, instructions, or disable code temporarily.

✅ Best way to comment out Java or dynamic code in JSP.

Example:

<%-- 
    <% String username = request.getParameter("username"); %> 
    <%= username %> 
--%>

Neither the Java code nor the output will be included in the HTML response.

If you’re inside a Java block (<% %>), you can use normal Java comments:

<%
    // This is a single-line Java comment
    int counter = 0;
%>

Multi-line Java comment:

<%
    /* This is
       a multi-line
       Java comment */
    int counter = 0;
%>

Comment Type	Syntax	Visible in Browser?	Purpose
HTML Comment	`<!-- comment -->`	✅ Yes	Client-side notes
JSP Comment	`<%-- comment --%>`	❌ No	Server-side notes
Java Comment	`//` or `/* */` inside `<% %>`	❌ No	Comment inside Java code block

Use  for HTML comments.
Use <%-- ... --%> for server-side JSP comments (best for hiding logic from browser).
Use // or /* */ when writing inside <% %> scriptlet blocks.