For static information (Web pages for examples), that not change frequently, esp8266 or esp32 have internal SPIFFS (SPI Flash File System) and you can upload data via Arduino IDE as explained in the article “WeMos D1 mini (esp8266), integrated SPIFFS Filesystem” but for fast operation and future support It’s usefully use FTP.
When you create a new IoT project probably you need to connect microcontroller to a battary power source, but if you don’t use a power saving options your battery will run out in no time.
As a lot of IoT microcontroller, WeMos D1 mini have some power saving mode.
The types are modem sleep, light sleep and deep sleep.
Library to use i2c pcf8575 IC with arduino and esp8266.
This IC can control (until 16) digital devices like button or led with 2 only pins.
Can read and write digital value with only 2 wire (perfect for ESP-01).
I try to simplify the use of this IC, with a minimal set of operation.