This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The Large-Allocation response header tells the browser that the page being loaded is going to want to perform a large allocation.

WebAssembly or asm.js applications can use large contiguous blocks of allocated memory. For complex games, for example, these allocations can be quite large, sometimes as large as 1GB. The Large-Allocation tells the browser that the web content in the to-be-loaded page is going to want to perform a large contiguous memory allocation and the browser can react to this header by starting a dedicated process for the to-be-loaded document, for example.

Header type Response header
Forbidden header name no


Large-Allocation: 0
Large-Allocation: <megabytes>


0 is a special value which represents uncertainty as to what the size of the allocation is.
The expected size of the allocation to be performed, in megabytes.


Large-Allocation: 0
Large-Allocation: 500


Not part of any current specifications. An explainer of the ideas behind this header can be found in this document.

Browser compatibility

Feature Chrome Edge Firefox Internet Explorer Opera Safari Servo
Large-AllocationNo supportNo support53No supportNo supportNo supportNo support
Feature Android Chrome for Android Edge Mobile Firefox for Android IE Mobile Opera Mobile Safari Mobile
Large-AllocationNo supportNo supportNo supportNo supportNo supportNo supportNo support

See also

Document Tags and Contributors

 Contributors to this page: fscholz
 Last updated by: fscholz,