ESP8266 has basic filesystem support, have a look at this: https://arduino-esp8266.readthedocs.io/en/latest/filesystem..... You define the filesystem's size when you flash the ESP and there's a tool to upload files there. You should also be able to find example projects that serve a webpage read from SPIFFS. Edit: this is a fake AP for esp8266 that I wrote some time ago that has a captive portal that loads pages from SPIFFS if they're there, otherwise sends some default pages directly from code https://github.com/GTP95/CaptivePortalMatematico?files=1