Commit hash using React and AWS Amplify

3 September 2020

Something I found out how to do today.


Suppose you want to display the hash of the commit where the app was built, perhaps on an about page or in the footer.


Follow these steps:

1. Modify the build script

2. Read the value in your app

3. Set up the value in development


In the above, REACT_APP_COMMIT_ID is the name of an environment variable to be used at build time (more details). It's important that its name starts with REACT_APP, as otherwise React won't be able to see its value (this is a security feature to avoid accidentally exposing secrets).

In part 1, we set its value to $AWS_COMMIT_ID. This is a reference to an Amplify build-time environment variable containing the hash of the commit being built. There are a number of environment variables automatically set by Amplify (see here), and you can even set your own (see here).