---
name: "nix-store-optimise"
section: "1"
platform: "linux"
package: "nix-bin"
version: "2.26.3+dfsg-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/nix-store-optimise"
---

# nix-store-optimise(1)

reduce disk space usage

## Name

`nix-store --optimise` - reduce disk space usage

### Synopsis

`nix-store` `--optimise`

### Description

The operation `--optimise` reduces Nix store disk space usage by finding identical files in the store and hard-linking them to each other. It typically reduces the size of the store by something like 25-35%. Only regular files and symlinks are hard-linked in this manner. Files are considered identical when they have the same Nix Archive (NAR) ⟨@docroot@/store/file-system-object/content-address.md#serial-nix-archive⟩ serialisation: that is, regular files must have the same contents and permission (executable or non-executable), and symlinks must have the same contents.

After completion, or when the command is interrupted, a report on the achieved savings is printed on standard error.

Use `-vv` or `-vvv` to get some progress indication.

{{#include ./opt-common.md}}

{{#include ../opt-common.md}}

{{#include ../env-common.md}}

### Example

```
$ nix-store --optimise
hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
...
541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
there are 114486 files with equal contents out of 215894 files in total
```