---
title: WindowBase64.atob()
slug: Web/API/WindowOrWorkerGlobalScope/atob
translation_of: Web/API/WindowOrWorkerGlobalScope/atob
original_slug: Web/API/WindowBase64/atob
---
<p>{{APIRef}}</p>

<p>La función <strong>WindowBase64.atob() </strong>descodifica una cadena de datos que ha sido codificada utilizando la codificación en base-64. Puedes utilizar el método {{domxref("window.btoa()")}} para codificar y transmitir datos que, de otro modo podrían generar problemas de comunicación. Luego de ser transmitidos se puede usar el método window.atob() para decodificar los datos de nuevo. Por ejemplo, puedes codificar, transmitir y decodificar los caracteres de control como valores ASCII 0 a 31.</p>

<p>For use with Unicode or UTF-8 strings, see <a href="/en-US/docs/Web/JavaScript/Base64_encoding_and_decoding#The_.22Unicode_Problem.22">this note at Base64 encoding and decoding</a> and <a href="/en-US/docs/Web/API/window.btoa#Unicode_Strings">this note at <code>window.btoa()</code></a>.</p>

<h2 id="Syntax" name="Syntax">Syntax</h2>

<pre class="syntaxbox">var decodedData = window.atob(<em>encodedData</em>);</pre>

<h2 id="Example" name="Example">Example</h2>

<pre class="brush:js">var encodedData = window.btoa("Hello, world"); // encode a string
var decodedData = window.atob(encodedData); // decode the string</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{SpecName('HTML WHATWG', '#dom-windowbase64-atob', 'WindowBase64.atob()')}}</td>
   <td>{{Spec2('HTML WHATWG')}}</td>
   <td>No change since the latest snapshot, {{SpecName("HTML5.1")}}.</td>
  </tr>
  <tr>
   <td>{{SpecName('HTML5.1', '#dom-windowbase64-atob', 'WindowBase64.atob()')}}</td>
   <td>{{Spec2('HTML5.1')}}</td>
   <td>Snapshot of {{SpecName("HTML WHATWG")}}. No change.</td>
  </tr>
  <tr>
   <td>{{SpecName("HTML5 W3C", "#dom-windowbase64-atob", "WindowBase64.atob()")}}</td>
   <td>{{Spec2('HTML5 W3C')}}</td>
   <td>Snapshot of {{SpecName("HTML WHATWG")}}. Creation of <code>WindowBase64</code> (properties where on the target before it).</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility" name="Browser_compatibility">Browser compatibility</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop(1)}}[1][2]</td>
   <td>10</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoMobile(1)}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<p>[1]  <code>atob()</code> is also available to XPCOM components implemented in JavaScript, even though <code><a href="/en-US/docs/DOM/window">window</a></code> is not the global object in components.</p>

<p>[2] Starting with <a href="/en-US/Firefox/Releases/27/Site_Compatibility">Firefox 27</a>, this <code>atob()</code> method ignores all space characters in the argument to comply with the latest HTML5 spec. ({{ bug(711180) }})</p>

<h2 id="See_also" name="See_also">See also</h2>

<ul>
 <li><a href="/Web/API/WindowBase64/Base64_encoding_and_decoding">Base64 encoding and decoding</a></li>
 <li><a href="/en-US/docs/data_URIs"><code>data</code> URIs</a></li>
 <li>{{domxref("window.btoa()")}}</li>
 <li><a href="/en-US/docs/Components.utils.importGlobalProperties">Components.utils.importGlobalProperties</a></li>
</ul>