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---
title: File
slug: Web/API/File
tags:
- API
- File API
- Interface
- NeedsTranslation
- Reference
- TopicStub
- Web
translation_of: Web/API/File
---
<div>{{APIRef}}</div>
<p>The <strong><code>File</code></strong> interface provides information about files and allows JavaScript in a web page to access their content.</p>
<p><code>File</code> objects are generally retrieved from a {{domxref("FileList")}} object returned as a result of a user selecting files using the {{HTMLElement("input")}} element, from a drag and drop operation's {{domxref("DataTransfer")}} object, or from the <code>mozGetAsFile()</code> API on an {{domxref("HTMLCanvasElement")}}. In Gecko, privileged code can create <code>File</code> objects representing any local file without user interaction (see {{anch("Implementation notes")}} for more information.)</p>
<p>A <code>File</code> object is a specific kind of a {{domxref("Blob")}}, and can be used in any context that a Blob can. In particular, {{domxref("FileReader")}}, {{domxref("URL.createObjectURL()")}}, {{domxref("ImageBitmapFactories.createImageBitmap()", "createImageBitmap()")}}, and {{domxref("XMLHttpRequest", "", "send()")}} accept both <code>Blob</code>s and <code>File</code>s.</p>
<p>See <a href="/en-US/docs/Using_files_from_web_applications">Using files from web applications</a> for more information and examples.</p>
<p>{{InheritanceDiagram}}</p>
<h2 id="Constructor">Constructor</h2>
<dl>
<dt>{{domxref("File.File", "File()")}}</dt>
<dd>Returns a newly constructed <code>File</code>.</dd>
</dl>
<h2 id="Properties">Properties</h2>
<dl>
<dt>{{domxref("File.lastModified")}} {{readonlyinline}}</dt>
<dd>Returns the last modified time of the file, in millisecond since the UNIX epoch (January 1st, 1970 at Midnight).</dd>
<dt>{{domxref("File.lastModifiedDate")}} {{readonlyinline}} {{deprecated_inline}} {{gecko_minversion_inline("15.0")}}</dt>
<dd>Returns the last modified <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date">Date</a></code> of the file referenced by the <code>File</code> object.</dd>
<dt>{{domxref("File.name")}} {{readonlyinline}}</dt>
<dd>Returns the name of the file referenced by the <code>File</code> object.</dd>
<dt>{{domxref("File.webkitRelativePath")}} {{readonlyinline}} {{non-standard_inline}}</dt>
<dd>Returns the path the URL of the {{domxref("File")}} is relative to.</dd>
</dl>
<p><code>File</code> implements {{domxref("Blob")}}, so it also has the following properties available to it:</p>
<dl>
<dt>{{domxref("File.size")}} {{readonlyinline}}</dt>
<dd>Returns the size of the file in bytes.</dd>
<dt>{{domxref("File.type")}} {{readonlyinline}}</dt>
<dd>Returns the <a href="/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types">MIME </a>type of the file.</dd>
</dl>
<h2 id="Methods">Methods</h2>
<p><em>The <code>File</code> interface doesn't define any methods, but inherits methods from the {{domxref("Blob")}} interface:</em></p>
<dl>
<dt>{{domxref("Blob.slice()", "Blob.slice([start[, end[, contentType]]])")}}</dt>
<dd>Returns a new <code>Blob</code> object containing the data in the specified range of bytes of the source <code>Blob</code>.</dd>
</dl>
<h2 id="Specifications">Specifications</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('File API')}}</td>
<td>{{Spec2('File API')}}</td>
<td>Initial definition</td>
</tr>
</tbody>
</table>
<h2 id="Browser_compatibility">Browser compatibility</h2>
<div>
<p>{{Compat("api.File")}}</p>
</div>
<p> </p>
<h3 id="Implementation_notes">Implementation notes</h3>
<ul>
<li>In Gecko, you can use this API from within chrome code. See <a href="/en-US/docs/Extensions/Using_the_DOM_File_API_in_chrome_code">Using the DOM File API in chrome code</a> for details. To use it from chrome code, JSM, and Bootstrap scope, you have to import it using <code><a href="/en-US/docs/Components.utils.importGlobalProperties">Cu.importGlobalProperties</a>(['File']);</code></li>
<li>Starting from Gecko 6.0 {{geckoRelease("6.0")}}, privileged code (such as extensions) can pass an {{interface("nsIFile")}} object to the DOM <code>File</code> constructor to specify the file to reference.</li>
<li>Starting from Gecko 8.0 {{geckoRelease("8.0")}}, you can use <code>new File</code> to create <code>File</code> objects from XPCOM component code instead of having to instantiate the {{interface("nsIDOMFile")}} object directly. The constructor takes, in contrast to {{domxref("Blob")}}, as second argument the filename. The filename can be any String.
<pre class="syntaxbox">new File(
Array parts,
String filename,
BlobPropertyBag properties
);</pre>
</li>
<li>The following non-standard properties and methods were removed in Gecko 7 {{geckoRelease("7.0")}}: {{domxref("File.fileName")}}, {{domxref("File.fileSize")}}, {{domxref("File.getAsBinary()")}}, {{domxref("File.getAsDataURL()")}}, {{domxref("File.getAsText()","File.getAsText(string encoding)")}} ({{bug("661876")}}). Standard properties {{domxref("File.name")}}, {{domxref("Blob.size")}}, and methods on {{domxref("FileReader")}} should be used instead.</li>
</ul>
<h2 id="See_also">See also</h2>
<ul>
<li><a href="/en-US/docs/Web/API/File/Using_files_from_web_applications">Using files from web applications</a></li>
<li>{{domxref("FileReader")}}</li>
<li><a href="/en-US/docs/Extensions/Using_the_DOM_File_API_in_chrome_code">Using the DOM File API in chrome code</a> (for privileged code running in Gecko, such as Firefox add-ons)</li>
</ul>
|
