Skip to content


Repository files navigation

Compare HAR files

Make it easier to find regressions by comparing your HAR files. Test it out or look at the video:


First: Shout out!

We couldn't built compare without the support or inspiration from the following people:

If you like our project, please give them also some extra love :)


Compare two different HAR files

How it works

As long as your HAR files follow the HAR specification you can use them in Compare. Standard HARs will give you some basic functionality and HARs from WebPageTest and will give you more.

HARs from Firefox/Chrome/Safari (and other browsers).

For all HARs we will show the waterfall (using PerfCascade) and statistics for the page (using PageXray).


If you add a WebPageTest HAR we will show SpeedIndex and FirstVisualChange and if you used Chrome to collect CPU stats, we will show that too. You will get some extra sugar if your HAR is from WebPageTest! Do you have something else that we should add? Create an issue or send a PR!

If you want even more sugar, you should use HAR files from or Browsertime: SpeedIndex, FirstVisualChange, LastVisualChange and a graph for VisualProgress.

If you deploy your result from your run to a server and use --resultBaseURL when you run, we will also pickup the screenshot, video and a link to the result page.

If you also run with --firstParty (adding a regex that show which assets that are first/third parties) we will will show data grouped by party.

First Party vs Third Party!

How to use it

You can either upload two HAR files (drag/drop) or give the URL to two URLs hosted online. If your HAR got multiple pages/runs, you can use just one HAR file.

Or you can just copy/paste your HAR file into the start page of

If you host your result pages, you can copy/paste the URL to a page or to a specific run and Compare will automagically find the URL to the HAR file.


You can use a configuration JSON to choose which HAR files that will be tested. The minimal configuration needed:

  "har1": {
    "url": ""
  "har2": {
    "url": ""

But you can also add some extra sugar. All the extras are optional:

  "har1": {
    "url": "",
    "label": "Before change",
    "run": 1
  "har2": {
    "url": "",
    "label": "After change",
    "run": 2
  "title": "The page title used in the title bar",
  "firstParty" : " (.*wikipedia.*||.*wikimedia.*)", // RegEx that defines first party requests
  "comments": {
    "intro": "Extra information put at the top of the page",
    "waterfall": "Text displayed at top of the waterfall",
    "visualProgress": "Text displayed at the top of visual progress",
    "domains": "Text displayed at the top of domains",
    "requestDiff": "Text displayed at the top of request/response diff",
    "firstParty": "Text displayed at the top of first/third party"

And then you can use your configuration file in different ways. You can copy/paste the configuration into the start page of

Or you can use it like this:

Make sure that your server has correct CORS settings so that can get the HAR file.

Github gist

You can also use host your configuration file on a Github gist and use the gist id to get the configuration file.

You can checkout out our example:

You can also copy/paste gist id (or the full URL to the gist) into

Thank you Matt Hobbs for sharing the gist idea!

Compare on the fly

You can also compare two HAR files on the fly without using a configuration file.

Add the parameters ?har1=FULL_URL1&har2=FULL_URL2&compare=1 and the two HAR files will be compared.


To run the project locally start a server with:

npm run develop

Send us a PR/create an issue. If you have big change coming up, please discuss it with us in an issue first!

Deploy your own version

Deploying your own version is easy:

  1. Clone the repo: git clone
  2. Build: cd compare && npm run build
  3. Copy everything in build/ to your server


We take your privacy really serious: We do not use any tracking software at all (no Google Analytics or any other tracking software) in The page do no call home.

And you can deploy your own version of if you want to be 100% in control.

Be kind

If you deploy your own version: please keep the original logo and the link to the project. We have spent a lot of our free time to work on this!

The logo

The compare logo (and the rest of the logos) are made by Mochamad Arief, you can find his stuff at