coach-core/lib/har/performance/headerSize.js

Core package for the Coach.

'use strict';

let util = require('../util');

module.exports = {
  id: 'headerSize',
  title: "Response headers should't be too big [HTTP/1]",
  description:
    'Avoid a lot of cookies and other stuff that makes your headers big when you use HTTP/1 because the headers are not compressed. You will send extra data to the user.',
  weight: 4,
  tags: ['performance', 'mobile'],
  processPage: function (page) {
    // H2 sends headers compressed and we don't get the right size now
    // so it's better just to skip those
    if (util.isHTTP2(page)) {
      return {
        score: 100,
        offending: [],
        advice:
          "The page uses an HTTP/2 connection and the headers are sent compressed, that's good. The current coach version cannot say if the size is good or not."
      };
    } else if (util.isHTTP3(page)) {
      return {
        score: 100,
        offending: [],
        advice:
          "The page uses an HTTP/3 connection and the headers are sent compressed, that's good. The current coach version cannot say if the size is good or not."
      };
    } else {
      let limit = 20000;
      let score = 100;
      let offending = [];
      page.assets.forEach(function (asset) {
        if (asset.headerSize > limit) {
          offending.push(asset.url);
          score -= 10;
        }
      });
      return {
        score: Math.max(0, score),
        offending: offending,
        advice:
          score < 100
            ? 'The page has ' +
              util.plural(offending.length, 'response') +
              ' with a header size larger than ' +
              util.formatBytes(limit) +
              '. You should really look into how to minimize the number of cookies sent.'
            : ''
      };
    }
  }
};