WorkerGlobalScope: btoa() method

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

Note: This feature is only available in Web Workers.

The btoa() method of the WorkerGlobalScope interface creates a Base64-encoded ASCII string from a binary string (i.e., a string in which each character in the string is treated as a byte of binary data).

You can use this method to encode data which may otherwise cause communication problems, transmit it, then use the WorkerGlobalScope.atob() method to decode the data again. For example, you can encode control characters such as ASCII values 0 through 31.

Syntax

btoa(stringToEncode)

Parameters

stringToEncode: The binary string to encode.

Return value

An ASCII string containing the Base64 representation of stringToEncode.

Exceptions

InvalidCharacterError DOMException: The string contained a character that did not fit in a single byte. See "Unicode strings" below for more detail.

Examples

const encodedData = self.btoa("Hello, world"); // encode a string
const decodedData = self.atob(encodedData); // decode the string

Unicode strings

Base64, by design, expects binary data as its input. In terms of JavaScript strings, this means strings in which the code point of each character occupies only one byte. So if you pass a string into btoa() containing characters that occupy more than one byte, you will get an error, because this is not considered binary data.

For more information and workarounds see Window.btoa().

Specifications

Specification
HTML Standard # dom-btoa-dev

Browser compatibility

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