crux-api

A tiny CrUX API wrapper that supports record & history API, handles errors, and provides types.

Motivation: CrUX API is a fantastic tool to get RUM data without installing any script. While using the API in Treo, we discovered a few complex cases like API errors, rate limits, not found entries, URLs normalization, and TypeScript notations. We decided to build the crux-api library to make working with the CrUX API easier.

Features:

• A tiny (500 bytes) wrapper for Chrome UX Report API;
• Supports both the record & history API;
• TypeScript notations for options and responses;
• Isomorphic: works in a browser and node.js;
• Returns null for the 404 (CrUX data not found) response;
• Automatic retry when hits the API rate limits: 429 (Quota exceeded);
• URL normalization helper to check the CrUX API index;

Usage

Install:

npm install crux-api

Fetch URL-level data for a various form factors and connections:

import { createQueryRecord } from 'crux-api'
const queryRecord = createQueryRecord({ key: CRUX_API_KEY })

// fetch all dimensions
const jsonRecord = await queryRecord({ url: 'https://github.com/marketplace?type=actions', formFactor: 'DESKTOP' })

The jsonRecord is null or an object with queryRecord response body, ex:

{
  "record": {
    "key": {
      "formFactor": "DESKTOP",
      "url": "https://github.com/marketplace"
    },
    "metrics": {
      "first_contentful_paint": {
        "histogram": [
          { "start": 0, "end": 1000, "density": 0.454180602006688 },
          { "start": 1000, "end": 3000, "density": 0.52575250836120291 },
          { "start": 3000, "density": 0.020066889632107024 }
        ],
        "percentiles": {
          "p75": 1365
        }
      },
      "cumulative_layout_shift": { ... },
      "first_input_delay": { ... },
      "largest_contentful_paint": { ... },
      "interaction_to_next_paint": { ... },
      "experimental_time_to_first_byte": { ... },
    }
  },
  "urlNormalizationDetails": {
    "originalUrl": "https://github.com/marketplace?type=actions",
    "normalizedUrl": "https://github.com/marketplace"
  }
}

Fetch historic data for a URL:

import { createQueryRecord } from 'crux-api'
const queryRecord = createQueryHistoryRecord({ key: CRUX_API_KEY })

const jsonHistory = await queryRecord({ url: 'https://www.github.com/' }) // fetch ALL_FORM_FACTORS

The jsonHistory is null or an object with queryRecord response body, ex:

{
  "record": {
    "key": {
      "url": "https://github.com/"
    },
    "metrics": {
      "cumulative_layout_shift": {
        "histogramTimeseries": [
          {
            "start": "0.00",
            "end": "0.10",
            "densities": [0.716522216796875, 0.672149658203125, ...]
          },
          {
            "start": "0.10",
            "end": "0.25",
            "densities": [0.244537353515625, 0.246917724609375, ...]
          },
          {
            "start": "0.25",
            "densities": [0.0389404296875, 0.0809326171875, ...]
          }
        ],
        "percentilesTimeseries": {
          "p75s": ["0.10", "0.12", ...]
        }
      },
      "experimental_time_to_first_byte": { ... },
      "first_contentful_paint": { ... },
      "first_input_delay": { ... },
      "interaction_to_next_paint": { ... },
      "largest_contentful_paint": { ... }
    }
  }
}

API

createQueryRecord(createOptions)

Returns a queryRecord function.

• createOptions.key (required) - CrUX API key, use https://goo.gle/crux-api-key to generate a new key;
• createOptions.fetch (optional, default: window.fetch) - pass a WHATWG fetch implementation for a non-browser environment;

queryRecord(queryOptions)

Fetches CrUX API using queryRecord options:

• queryOptions.url or queryOptions.origin (required) – the main identifier for a record lookup;
• queryOptions.formFactor (optional, defaults to all form factors) - the form factor dimension: PHONE | DESKTOP | TABLET;
• queryOptions.effectiveConnectionType (optional, defaults to all connections) - the effective network class: 4G | 3G | 2G | slow-2G | offline.

Returns a Promise with a raw queryRecord response or null when the data is not found.

import { createQueryRecord } from 'crux-api'

const queryRecord = createQueryRecord({ key: process.env.CRUX_API_KEY })
const res = await queryRecord({
  url: 'https://github.com/marketplace?type=actions',
  formFactor: 'DESKTOP',
  effectiveConnectionType: '4G',
})

// res -> URL-level data for https://github.com/marketplace

createQueryHistoryRecord(historyOptions)

Returns a function that fetches [CrUX History API using queryHistoryRecord options:

import { createQueryHistoryRecord } from 'crux-api'

const queryHistory = createQueryHistoryRecord({ key: process.env.CRUX_API_KEY })
const res = await queryHistory({
  url: 'https://www.github.com/',
})

normalizeUrl(url)

Normalize a URL to match the CrUX API internal index. It is a URL's origin + pathname (source).

import { normalizeUrl } from 'crux-api'

console.log(normalizeUrl('https://github.com/marketplace?type=actions')) // https://github.com/marketplace (removes search params)
console.log(normalizeUrl('https://github.com')) // https://github.com/ (adds "/" to the end)

CrUX API Responses

The crux-api is designed to return data and automatically handles errors. It returns an object for 200 responses, retries after 429, and returns null for 404. For 400 and 5xx it throws a relevant error.

Below are all known responses of Chrome UX Report API for easier debugging and development (The API documentation is vague about errors, please, submit an issue, if you know other responses).

Credits

Sponsored by Treo - Page speed monitoring made simple.