Udaan Institute

What is ASP Buffering?

In Classic ASP (Active Server Pages), buffering is the process of storing all response output in memory on the server before it’s sent to the client’s browser. This means that nothing is sent to the browser until the script finishes running (or buffering is manually flushed).

Why Use Buffering in ASP?

Buffering gives developers control over what gets sent to the client and when. This is important because:

1. HTTP Headers Must Be Sent First
   In ASP, you can’t modify HTTP headers (like Response.Status or Response.ContentType) after output has started going to the browser. Buffering ensures output is delayed so you can change headers at any time during execution.
2. Error Handling
   If an error occurs in the middle of script execution, buffering allows the server to suppress partial or incorrect output and send a custom error message instead.
3. Performance Optimization
   Sending fewer, larger responses can reduce the number of HTTP packets and improve performance in certain cases.

How to Enable or Disable Buffering

You can control buffering using the Response.Buffer property:

<% Response.Buffer = True %>   ' Enables buffering
<% Response.Buffer = False %>  ' Disables buffering

Important: Response.Buffer = True must be placed before any output is written to the response, otherwise it will cause an error.

Flushing the Buffer

If you want to manually send the buffered output before the script ends, you can use:

<% Response.Flush() %>

This flushes the buffer — sending its contents to the browser — but keeps buffering enabled so you can still send more output later.

Disabling Buffering: When and Why?

You might disable buffering if:

• You want to stream output to the user in real time (e.g., for progress indicators).
• You’re debugging and want to see output immediately.
• Your script produces very large output and you don’t want to risk high memory usage on the server.

Summary