```{eval-rst}
.. role:: bash(code)
   :language: bash
```

```{eval-rst}
.. role:: js(code)
   :language: javascript
```

```{eval-rst}
.. role:: python(code)
   :language: python
```

# How Migrations Are Run on l10n Repositories

Once a patch including new FTL strings and a migration recipe lands in
`mozilla-firefox`, the Localization Team will perform a series of actions to migrate
strings for all 100+ localizations:

- New Fluent strings land in `mozilla-firefox`, together with a migration
  recipe.
- New strings are added to an `update` branch of [firefox-l10n-source],
  a unified repository including strings for all shipping versions of Firefox,
  and used as a buffer before exposing strings to localizers.
- Migration recipes are run against all l10n subfolders, migrating strings
  from old to new files, and storing them in VCS.
- New en-US strings are merged into the `main` branch of `firefox-l10n-source`
  that syncs with localization tools, exposing strings to all localizers.

Migration recipes could be run multiple times within a release cycle if more
patches containing migrations land after the first.

Migration recipes are periodically removed from `mozilla-firefox`. This clean-up
process will typically leave recipes from the most recent 2 or 3 cycles. Older
recipes are stored in [this repository] .

:::{tip}
A script to run migrations on all l10n repositories is available in [this
repository][this repository], automating part of the steps described for manual testing, and
it could be adapted to local testing.
:::

[firefox-l10n-source]: https://github.com/mozilla-l10n/firefox-l10n-source/
[this repository]: https://github.com/flodolo/fluent-migrations