Encode Strings rewrites string literals into escaped character sequences so the original text is less readable in the output file.
Example
A readable string such as "tabIndex" can be rewritten as "\x74\x61\x62\x49\x6E\x64\x65\x78".
if (d === "\x74\x61\x62\x49\x6E\x64\x65\x78") {
var b = c.getAttributeNode("\x74\x61\x62\x49\x6E\x64\x65\x78");
}
When to use it
This is a lightweight way to make important string literals less obvious in the output. It is often combined with other options such as Name Mangling or Move Strings Into Array.
Important: if SelfCompression is enabled, this option does not have the same practical effect because the final script is already packed into a compressed wrapper.