# Building Firefox 32-bit On Linux 64-bit

:::{note}
Unless you really want to target older hardware, you probably
want to {ref}`Build Firefox 64-bit <building-firefox-on-linux>`
since it is better-supported.
:::

Before following these 32-bit-Firefox-specific instructions, follow
the {ref}`building-firefox-on-linux` instructions to ensure that
your machine can do a normal build.

## Instructions for Ubuntu 19.10

These steps were verified to work as of June 2020.

1. Run `rustup target install i686-unknown-linux-gnu` to install the
   32-bit Rust target.
2. Install 32-bit dependencies with the following command (this shouldn't try to
   remove packages. If this is the case, those instructions won't work as-is):

```
sudo apt install gcc-multilib g++-multilib \
  libgtk2.0-dev:i386 libgtk-3-dev:i386 libpango1.0-dev:i386 libxt-dev:i386 \
  libx11-xcb-dev:i386 libpulse-dev:i386 libdrm-dev:i386
```

1. Then, create a `mozconfig` file in your Firefox code directory
   (probably `firefox`) that looks like the following example:

   ```
   ac_add_options --target=i686
   ```

2. Run `./mach build`.