Toby Gates.
Automatically adding size labels to your GitHub PRs

Automatically adding size labels to your GitHub PRs

By Toby Gates - 29 December 2023


Recently i've found it useful to add size labels to PRs. This has allowed my colleages and I to quickly see which PRs are large and which are small, allowing us to prioritise the larger PRs first.

It also allowed us to track the size of our PRs over time, which was useful for spotting trends and identifying areas for improvement.

In this article I'll show you how to get setup with the GitHub action we've setup that will automatically add size labels to your PRs.

Setting up the action

To add size labels to your PRs you'll need to create a GitHub action. This action will run whenever a PR is opened or updated and will add a label to the PR based on the number of lines changed.

To use the action that I've created, you'll need to add a new action to your .github/workflows/ directory.

Create a new file called pr-auto-label-action.yml and add the following code:

name: PR Auto Label Action
      - opened
      - edited
      - synchronize
      - labeled
      - unlabeled
    runs-on: ubuntu-latest
      pull-requests: write
      - uses: tobytheghost/pr-auto-label-action@main
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

This will run the action whenever a PR is opened, edited, synchronised, labelled or unlabelled. It will also give the action permission to write to the PR.

You can mark files as ignored by adding the IGNORED_FILES environment variable (next to the GITHUB_TOKEN variable). This should be a space separated list of file names.

For example, if you wanted to ignore package-lock.json and yarn.lock you would add the following to your workflow file:

  IGNORED_FILES: package-lock.json yarn.lock

How it works

The action uses the GitHub API to get the number of lines changed in the PR. It then uses this number to determine which label to add to the PR.

The following labels will be added to your Pull Requests depending on their size:

  • size/XS - 1 - 50 lines
  • size/S - 51 - 100 lines
  • size/M - 101 - 250 lines
  • size/L - 251 - 500 lines
  • size/XL - 501 - 1000 lines
  • size/XXL - 1001+ lines


I hope you find this action as useful as I have.

If you have any questions or suggestions, please feel free to drop me a message via my socials or through the contact form!

You can find the source code for the action here: tobytheghost/pr-auto-label-action.