Overweight

An all-in-one toolkit for keeping your bundle sizes in check. It ships with a CLI, Node API, and GitHub Action, plus a tester architecture that lets you decide how assets are evaluated.

Highlights

• Drop-in configuration: define overweight entries in package.json or overweight.config.json.
• Works everywhere: CLI, Node API, and an official reusable GitHub Action.
• Extensible testers: start with gzip (default), brotli, or none, and plug in your own logic programmatically.
• Globs & multi-match aware: every file matched by a glob is tracked individually.
• Conventional commits + semantic-release driven publishing with automatic changelog generation.
• Modern successor to the original bundlesize: migration is trivial, yet the project stands on its own roadmap.

Installation

pnpm add -D overweight

Configuration

Keep your configuration close to your code:

• overweight.json (or overweight.config.json) at the project root (default when the CLI runs without args).
• package.json → overweight field (array or object with a files property).
• Any JSON file referenced via overweight --config path/to/config.json.

{
  "files": [
    {
      "path": "./dist/vendor.js",
      "maxSize": "30 kB",
      "compression": "gzip",
      "label": "Vendor bundle"
    },
    {
      "path": "./dist/chunk-*.js",
      "maxSize": "10 kB",
      "compression": "brotli"
    }
  ]
}

Field reference:

| Field | Type | Description | | ------------ | --------------- | --------------------------------------------------------------------------- | | path | string | File path or glob resolved from the config root. | | maxSize | string | number | Accepts units (10 kB, 2MiB). Numbers are treated as raw bytes. | | compression| string | Tester id (gzip, brotli, none). Defaults to gzip. | | label | string | Optional human-friendly label used in reports. |

CLI

pnpm overweight
pnpm overweight --config ./configs/overweight.json
pnpm overweight --reporter json

# quick ad-hoc checks
pnpm overweight --file "dist/*.js" --max-size "15 kB" --compression brotli

Available reporters: console (default), json, json-file, silent.

# emit a machine-readable report
pnpm overweight --reporter json-file --report-file ./reports/overweight.json

Node API

import { runChecks, normalizeConfig } from "overweight";

const config = normalizeConfig({
  files: [{ path: "./dist/app.js", maxSize: "15 kB", compression: "brotli" }]
});

const result = await runChecks(config, {
  testers: {
    custom: {
      id: "custom",
      label: "custom",
      async measure(buffer) {
        return { bytes: buffer.byteLength / 2 };
      }
    }
  }
});

if (result.stats.hasFailures) {
  throw new Error("Bundle too big!");
}

GitHub Action

name: bundle-overweight-test

on:
  pull_request:
  push:
    branches: [main]

jobs:
  overweight:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: pnpm/action-setup@v3
        with:
          version: 9
      - run: pnpm install
      - uses: yoavniran/overweight@v1
        with:
          config: overweight.json
          github-token: ${{ secrets.GITHUB_TOKEN }}
          baseline-report-path: overweight-report.json
          update-baseline: true
          report-file: overweight-report.json

• report-json, report-table, and report-file outputs enable downstream workflows (PR comments, Slack alerts, artifact uploads, etc.).
• When baseline-report-path + update-baseline are set, the action refreshes the stored bundle size report on the branch that ran the workflow. If baseline-report-path is omitted and report-file is set, the baseline defaults to that path. The update runs on a dedicated branch + pull request using update-pr-title, update-pr-body, and update-branch-prefix. Use baseline-protected-branches (default main,master, supports glob patterns) to block updates on protected branches.
• comment-on-pr-always (first run only) and comment-on-pr-each-run control when PR comments are posted even if checks pass.
• Additional outputs (report-file, baseline-updated, baseline-update-pr-url, baseline-update-pr-number) make it easy to chain artifact uploads or follow-up workflows.

Baseline auto-PR requirements

When update-baseline: true, Overweight will:

1. Regenerate the baseline snapshot locally.
2. Create a temporary branch from the PR's base branch.
3. Commit the updated baseline file with the bot identity.
4. Open a pull request targeting the base branch using the configured title/body.

To allow that flow:

• Ensure the workflow grants contents: write permission (GitHub defaults to read-only).
• Check out the repository with actions/checkout@v4 (fetch-depth defaults are fine because commits are created via the GitHub API).
• Pass a github-token secret with permission to create branches and PRs in the repository (the default secrets.GITHUB_TOKEN works for same-repo PRs).
• Optionally customize update-pr-title, update-pr-body, and update-branch-prefix to fit your repo conventions.
• In the repository settings go to Settings → Actions → General → Workflow permissions and enable Allow GitHub Actions to create and approve pull requests, otherwise GitHub will block the auto-PR.
• Overweight reuses the same update branch/PR per source PR (branch suffix pr-<number>), so subsequent pushes to your feature branch simply update the existing baseline PR instead of opening multiples.
• Use baseline-protected-branches to list branches or patterns (comma-separated) where baseline updates are forbidden; the default main,master protects the typical default branches.
• Manual workflows triggered on a feature branch automatically detect the open PR for that branch and reuse its baseline update PR instead of opening a new one.
• Baseline updates occur only when all size checks pass. Failing runs skip the baseline refresh entirely to avoid locking in broken results.

Release & contributing

• The project is ESM-only and built via tsup
• Conventional commits are enforced via simple-git-hooks + commitlint.
• pnpm run release triggers semantic-release, which:
  • Checks commit history,
  • Updates the changelog,
  • Publishes to npm,
  • Creates a GitHub release/tag.
• After each non-dry release run the workflow force-updates a moving major tag (e.g. v1) so consumers can reference yoavniran/overweight@v1 for the latest release in that major line.
• .github/workflows/release.yml exposes a dry-run workflow input (defaults to true) so manual dispatches preview semantic-release without mutating tags or npm. Set the field to false to publish for real, e.g.:

gh workflow run "Overweight Release" \
  --ref release-main \
  --field dry-run=false

Syncing tags

Since the release workflow force-updates major tags (e.g., v1), when syncing your local repository you may encounter tag conflicts. To sync tags properly:

# Recommended: Use the sync-tags script
pnpm run sync-tags

# Or manually force-update all tags from remote
git fetch --tags --force

# Alternative: Delete conflicting tag and re-fetch
git tag -d v1 && git fetch origin tag v1

MIT License © Yoav Niran.