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Composer out of memory (allowed memory size exhausted)
======================================================

### [\#PHP](https://rocketeersapp.com/knowledge/php)

Composer can run out of memory while resolving dependencies, especially on small VPSes. The real fix is usually swap space, not a bigger memory limit.

 Published by [Mark van Eijk](https://rocketeersapp.com/author/mark-van-eijk) on June 23, 2026 · 1 minute read

1. [About the error](#content-about-the-error)
2. [Why do I see this error](#content-why-do-i-see-this-error)
3. [Solution](#content-solution)
4. [Make sure you're on Composer 2](#content-make-sure-youre-on-composer-2)
5. [Add swap space (the proper fix on a small VPS)](#content-add-swap-space-the-proper-fix-on-a-small-vps)
6. [Raise the memory limit for one command](#content-raise-the-memory-limit-for-one-command)
7. [Prefer require over update where you can](#content-prefer-require-over-update-where-you-can)

[\#](#content-about-the-error "Permalink")About the error
---------------------------------------------------------

Running `composer update` or `composer require` fails with:

 ```
PHP Fatal error: Allowed memory size of 1610612736 bytes exhausted (tried to allocate ...)

```

Dependency resolution is memory-hungry. To pick compatible versions, Composer compares every candidate version of every package against all the others, and large or conflicted dependency trees can exhaust the available memory.

[\#](#content-why-do-i-see-this-error "Permalink")Why do I see this error
-------------------------------------------------------------------------

- A big dependency tree, or `composer update` resolving everything from scratch.
- A small server with little RAM and **no swap** configured.
- An old Composer 1.x install, version 1 used far more memory than version 2.

[\#](#content-solution "Permalink")Solution
-------------------------------------------

### [\#](#content-make-sure-youre-on-composer-2 "Permalink")Make sure you're on Composer 2

Composer 2 cut memory use dramatically. Check and upgrade:

 ```
composer --version
composer self-update --2

```

### [\#](#content-add-swap-space-the-proper-fix-on-a-small-vps "Permalink")Add swap space (the proper fix on a small VPS)

If `proc_open(): fork failed` or the out-of-memory error shows up on a low-RAM server, the machine simply has no headroom. Adding swap solves it durably without raising PHP limits. See the dedicated guide on [adding swap space on Ubuntu](/add-swap-space-on-ubuntu).

### [\#](#content-raise-the-memory-limit-for-one-command "Permalink")Raise the memory limit for one command

To get unblocked immediately, run Composer with an unlimited limit just for that invocation:

 ```
COMPOSER_MEMORY_LIMIT=-1 composer update

```

Or point Composer at a php.ini with a higher limit:

 ```
php -d memory_limit=-1 /usr/local/bin/composer update

```

### [\#](#content-prefer-require-over-update-where-you-can "Permalink")Prefer require over update where you can

`composer require some/package` resolves a smaller slice of the tree than a full `composer update`, and `composer install` against an existing `composer.lock` barely uses any memory at all. On production you should only ever run `composer install`, never `update`:

 ```
composer install --no-dev --optimize-autoloader

```

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