How does Laravel implement its Middleware Pipeline, and what is the TerminableMiddleware interface?

Short answer

It passes the request through a chain of wrapped Closures; Terminable Middleware provides terminate($request, $response), which runs after the response has been sent to the client.

Explanation

Middlewares rely on Illuminate\Pipeline\Pipeline. Each middleware receives $request and a $next function; it can inspect the request before calling $next($request), or modify the response when the call returns. If the Middleware implements terminate(), Laravel calls it after the client has received the full response, making it suitable for logging and metrics collection without delaying the user.

Code example

class LogRequest {
    public function handle($request, Closure $next) {
        return $next($request);
    }
    public function terminate($request, $response): void {
        // Runs after the response reaches the browser
        Log::info("Request finished with code: " . $response->status());
    }
}

Common mistakes

• Running long operations inside handle() after $next() instead of using terminate().

Follow-up questions

• What is the Laravel Request Lifecycle from arrival at public/index.php to the response being sent?

Sources

• Laravel docs — Middleware