NodeMCU ESP8266 contains a Serial Peripheral Interface Flash File System (SPIFFS). Here to shows how to easily upload files to the ESP8266 filesystem using a plugin for Arduino IDE.
SPIFFS lets you access the flash chip memory like you would do in a normal filesystem in your computer, but simpler and more limited. You can read, write, close, and delete files. SPIFFS doesn’t support directories, so everything is saved on a flat structure.
Using SPIFFS with the ESP8266 board is specially useful to:
Create configuration files with settings;
Save data permanently;
Create files to save small amounts of data instead of using a microSD card;
Save HTML and CSS files to build a web server;
Save images, figures and icons;
And much more.
In most of our web server projects, we’ve written the HTML code for the web server as a String directly on the Arduino sketch. With SPIFFS, you can write the HTML and CSS in separated files and save them on the ESP8266 filesystem.
Installing the ESP8266FS-0.4.0.zip
ESP8266FS is a plugin for the Arduino IDE that allows you to upload files directly to the ESP8266 filesystem from a folder in your computer.
Download Plugin here https://github.com/esp8266/arduino-esp8266fs-plugin/releases
Go to the Arduino IDE directory, and open the Tools folder
Unzip the downloaded .zip folder to the Tools folder. You should have a similar folder structure: