Chrome-har

Create HAR files based on Chrome DevTools Protocol data.

We got tired of waiting for the +30K engineers at Google implementing a way to automate to get a HAR file https://issues.chromium.org/issues/40809195 so we implemented our own solution in the mean time.

Code originally extracted from Browsertime, initial implementation inspired by Chromedriver_har.

Create a new bug report

Make sure to generate a event trace log file that we can use to recreate your issue. If you use Browsertime you can enable the trace with --chrome.collectPerfLog:

$ browsertime --chrome.collectPerfLog -n 1 https://www.sitespeed.io

Then take the file named chromePerflog-1.json.gz and put it in a gist or make it availible to us in any way you want.

If you use sitespeed.io:

$ sitespeed.io --browsertime.chrome.collectPerfLog -n 1 https://www.sitespeed.io

Stream messages

harFromMessages takes an array (or any iterable) of messages. If the messages come from a stream, use harFromMessagesAsync. It takes an async iterable, handles each message when it arrives and returns a promise for the HAR. You do not need to keep all messages in memory.

import { harFromMessagesAsync } from 'chrome-har';

const har = await harFromMessagesAsync(messageStream);

Support for Response Bodies

If you use Chrome-har standalone (without Browsertime/sitespeed.io) you can use get the response bodies in HARs if they are set on the response object by the caller and if the includeTextFromResponseBody option is set to true.

For example:

const harEvents: Array<any> = [];

client.on('Network.requestIntercepted', async (params: any) => {
  // Get the response body
  const response = await client.send(
    'Network.getResponseBodyForInterception',
    { interceptionId: params.interceptionId },
  );

  // Set the body on the response object
  if (params.response != null) {
    params.response.body = response.body;
  } else {
    params.response = response;
  }

  // Continue the request
  await client.send(
    'Network.continueInterceptedRequest',
    { interceptionId: params.interceptionId },
  );

  harEvents.push({ method, params });
});

const har = harFromMessages(harEvents, {includeTextFromResponseBody: true});