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Separate the wheat from the chaff in your build files!

Example PR Status

thresh is a CI integration for tracking file size changes across builds. Pluggable for different CI providers. (Currently plugins only exist for CircleCI.)

What it Does

At its core, thresh does two things:

  1. Outputs file sizes of files targeted by your thresh config. (Where and how these are output depends on the artifactStore plugin you use.)
  2. If the current bulid is associated with an existing PR, it posts a commit status. This status will be success if there are no target files which violate size thresholds defined in your thresh config, failure if there are target files which violate sizes thresholds, and error if any errors were encountered. The contents of this status will contain target diffs if they could be calculated.
Example target-sizes.json:
    "filepath": "example/dist/app1.js",
    "size": 53
    "filepath": "example/dist/app2.js",
    "size": 95
Example target-diffs.json:
  "diffs": [
      "targets": [
      "previous": 148,
      "current": 148,
      "difference": 0,
      "percentChange": 0
  "failures": []

CLI Options


  • Description: Filepath to your thresh conifg file.
  • Type: String
  • Default: ./.threshrc.toml


Create threshrc.toml File

A threshrc config file has the following format:

type Config = {
  thresholds :: [Threshold],
  artifactStore :: String,
  ciAdapter :: String


  • thresholds - A list of configuration objects used to determine the conditions under which the GitHub status will be posted as "failed."
  • artifactStore = '@danny-andrews/thresh-artifact-store-circleci' - The module name of the artifact store plugin you want to use. (Defaults to CircleCI.)
  • ciAdapter = '@danny-andrews/thresh-ci-adapter-circleci' - The module name of the CI adapter you want to use. (Defaults to CircleCI.)

With Threshold being:

type Threshold = {
  targets: String | [String],
  maxSize: Number


  • targets - The target(s) of the threshold. Each target can be either a file path or a glob.
  • maxSize - The max size of the total of all the files selected by targets.
Example config file:
targets = "dist/*.js"
maxSize = 20000

This example would post a failed GitHub status if the total size of all JavaScript files contained in the dist directory was larger than 20kB.

Define Environment Variables

    • Must have read access to repository (public_repo scope for public repos, and repo scope for private repos)
    • Must have repo:status scope

(Check out the README of the artifact store plugin you are using for any additional environment variable requirements.)

Comparison with Other Offerings

bundlesize buildsize thresh
Handles Fingerprinting? Y Y Y
Posts PR Status Filesize Diffs? Y Y Y
Relies on 3rd-party service? Y Y N
CIs Supported Travis CI, CircleCI, Wercker, and Drone Circle CI Circle CI, easy to add more
Configuration Expose GitHub access token to environment None Expose GitHub/CircleCI access token to environment

Writing plugins

ciAdapter Plugins

A valid thresh ci adapter is just a function which returns an object with the following type:

type CIAdapter = {
  isRunning :: () -> Boolean
  getEnvVars :: () -> EnvVars

type EnvVars = {
  buildSha :: String,
  buildUrl :: String,
  artifactsDirectory :: String,
  repoOwner :: String,
  repoName :: String,
  pullRequestId :: Maybe String

artifactStore Plugins

A valid thresh artifactStore is just a function which returns an object with the following type:

type ArtifactStore = {
  getTargetStats :: (baseBranch = String)
    -> (targetStatsFilepath = String)
    -> ReaderPromise TargetStat

type TargetStat = {
  filepath :: String,
  size :: Int

Future Plans

Create more plugins for different CI environments.


A CircleCI Plugin for posting bundle diffs to your GitHub PRs.







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