Error initializer-string for array of chars is too long using ESP32 Webserver
Please check the readme: https://github.com/me-no-dev/ESPAsyncWebServer#send-large-webpage-from-progmem
You probably have to declare it in progmem without rawliteral.
const​ ​char​ index_html[] PROGMEM = ​&quot;​...​&quot;​; ​//​ large char array, tested with 14k​ request-&gt;​send_P​(​200​, ​&quot;​text/html​&quot;​, index_html);