---
title: "b64decode( input, [encoding], [format] ) | Grafana k6 documentation"
description: "Base64 decode a string."
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

# b64decode( input, \[encoding], \[format] )

Decode the passed base64 encoded `input` string into the unencoded original input in either binary or string formats.

Expand table

| Parameter           | Type   | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|---------------------|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| input               | string | The string to base64 decode.                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| encoding (optional) | string | The base64 encoding to use.  <br />Available options are:  <br />\- **“std”**: the standard encoding with `=` padding chars and `+` and `/` characters in encoding alphabet. This is the default.  <br />\- **“rawstd”**: like `std` but without `=` padding characters.  <br />\- **“url”**: URL safe version of `std`, encoding alphabet doesn’t contain `+` and `/` characters, but rather `-` and `_` characters.  <br />\- **“rawurl”**: like `url` but without `=` padding characters. |
| format (optional)   | string | If `"s"` return the data as a string, otherwise if unspecified an ArrayBuffer object is returned.                                                                                                                                                                                                                                                                                                                                                                                            |

### Returns

Expand table

| Type                 | Description                                                                                                                   |
|----------------------|-------------------------------------------------------------------------------------------------------------------------------|
| ArrayBuffer / string | The base64 decoded version of the `input` string in either string or ArrayBuffer format, depending on the `format` parameter. |

### Example

JavaScript ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```javascript
import { check } from 'k6';
import encoding from 'k6/encoding';

export default function () {
  const str = 'hello world';
  const enc = 'aGVsbG8gd29ybGQ=';
  const expBin = new Uint8Array([104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100]);
  check(null, {
    'is decoding to string correct': () => encoding.b64decode(enc, 'std', 's') === str,
    'is decoding to ArrayBuffer correct': () => {
      const decBin = new Uint8Array(encoding.b64decode(enc));
      if (decBin.length != expBin.length) return false;
      for (let i = 0; i < decBin.length; i++) {
        if (decBin[i] !== expBin[i]) return false;
      }
      return true;
    },
  });
}
```