HTTP Headers: duolingo.cn

cache-control
content-encoding
content-type
date
expires
no-retry
pragma
server
set-cookie
surrogate-control
x-duo-request-host
x-envoy-upstream-service-time
x-frame-options
x-runtime
x-tid
x-ws

Strict-Transport-Security (HSTS) forces browsers to use HTTPS. Content-Security-Policy (CSP) prevents XSS attacks by controlling which resources can load. X-Content-Type-Options stops MIME-type sniffing. X-Frame-Options blocks clickjacking by preventing iframe embedding.

duolingo.cn's security score of 40/100 reflects how many of these protective headers are configured. Higher scores indicate better defense against common web attacks.