guide/source/2.12-migration.md
Most of the new features in Meteor 2.12 are either applied directly behind the scenes (in a backwards compatible manner) or are opt-in. For a complete breakdown of the changes, please refer to the changelog.
The above being said, there are a few items that you should implement to have easier time in the future.
<h3 id="old-api-warning">Old API Warning</h3>With our migration to the new async/await API, we have added a warning to the
old API. In order to use it, before running your application, set the
environment variable WARN_WHEN_USING_OLD_API to true. For example, you can
run the folling command in your application directory:
WARN_WHEN_USING_OLD_API=true meteor
It will run your app and every time you use the old API, you will see a warning in your console. This will help you find the places in your code that need to be updated.
If you are in doubt whether a particular API is old or new, you can check our v2.8 migration guide that lists all the changes in the new API.
<h2 id="older-versions">Migrating from a version older than 2.11?</h2>If you're migrating from a version of Meteor older than Meteor 2.11, there may be important considerations not listed in this guide. Please review the older migration guides for details: