Large-Allocation Header

Table of Content

The Large-Allocation header is an HTTP response header, designed to provide a signal to the browser that the forthcoming document will need a large amount of memory. This is especially useful for websites that house applications requiring a significant amount of memory, such as, but not limited to, online gaming applications, heavy data processing pages, or complex visual rendering sites.


The syntax for this specific header is straightforward, requiring only the descriptor followed by the amount of memory in question.

Large-Allocation: <amount-in-mb>


The only directive involved in the Large-Allocation header is <amount-in-mb>. This represents the amount of memory, in megabytes, that the browser should set aside for the relevant document.


Utilizing the Large-Allocation header is as simple as defining the expected memory requirement in the HTTP response:

Large-Allocation: 200

Here, we are telling the browser that the application will require around 200 megabytes of memory.

Browser Compatibility

Browser Compatibility
Chrome Not Supported
Firefox Supported
Safari Not Supported
Opera Not Supported
Edge Not Supported

Currently, only Firefox supports the Large-Allocation header.

How to modify Large-Allocation header

ModHeader is a popular Chrome extension used for modifying HTTP request and response headers. To manipulate the Large-Allocation header with ModHeader, follow these steps:

  1. Add the ModHeader extension to your Chrome browser.
  2. Open the extension by clicking on its icon next to the address bar.
  3. In the Response Headers section, click on '+ Add' to add a new header.
  4. Enter 'Large-Allocation' in the 'Name' field, then specify the amount of memory (e.g. '200') in the 'Value' field.

Please note that despite being able to modify the Large-Allocation header, Chrome does not currently support it - this modification would only be useful when simulating scenarios for supported browsers, like Firefox.