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# atob()

The **`atob()`** function decodes a
string of data which has been encoded using Base64 encoding. You can use
the `btoa()` method to encode and transmit
data which may otherwise cause communication problems, then transmit it and use the
`atob()` method to decode the data again. For example, you can encode,
transmit, and decode control characters such as ASCII values 0 through 31.

For use with Unicode or UTF-8 strings, see the note on "Unicode strings" in the page
for `btoa()`.

## Syntax

```js
atob(encodedData)
```

### Parameters

- `encodedData`
  - : A binary string (i.e., a string in which each character in the string is treated as a byte of binary data) containing base64-encoded data.

### Return value

An ASCII string containing decoded data from `encodedData`.

### Exceptions

- `InvalidCharacterError`
  - : Thrown if `encodedData` is not valid base64.
