What Makes Plain Text Portable
Plain text is portable because it contains only basic letters, numbers, and symbols that every computer system recognizes. Unlike fancy document formats that need special software to display colors, fonts, and images, plain text files are simple. Any device with any text editor can open and read a plain text file exactly the same way.
No Software Dependencies
Formatted documents like Word files or PDF files require specific programs to open correctly. Plain text files do not need any special software. You can open a plain text file on a computer made 20 years ago or a brand new smartphone, and it will display exactly the same.
Works Across All Operating Systems
Windows computers, Apple Macs, and Linux systems all handle plain text the same way. A plain text file created on one type of computer works perfectly on another type without any conversion needed. This makes plain text ideal for sharing information between different types of devices and systems.
Small File Size and Fast Transfer
Plain text files are very small compared to other document formats. This means they transfer quickly over the internet and take up minimal storage space. Because they contain no images, styling, or extra data, plain text files are efficient and easy to move between devices.
Long-Term Readability
Plain text files can be read by future generations because the format is so basic. Even if a specific software program becomes outdated or disappears, plain text will always be readable. This makes plain text a reliable format for preserving information over many years. 
Answer