Comments on: HAR to Page Speed

By: Mark Nottingham

Mark Nottingham — Wed, 05 May 2010 05:12:03 +0000

My thoughts ran on a bit, so I put them here:
http://www.mnot.net/blog/2010/05/05/har

Cheers,

By: Dawn

Dawn — Tue, 04 May 2010 19:58:10 +0000

Very happy to see more applications adopting the HAR format. One thing I would like to see is the ability to capture this information via tcpdump or Wireshark.

By: Sergey Chernyshev

Sergey Chernyshev — Tue, 04 May 2010 02:13:58 +0000

@Jennifer when I’m looking at scores, I see some way of quantifying best practices and providing tools that are independent from the location or CPU power of the computer that does measurements – this is very useful and actually not that easy to achieve. That being said, I believe, that understanding “precise” measurements is also important and it’d be great if there was some data about acceptable DNS speeds or time to draw/load events and so on.

@Steve it’s just amazing how SDK can be wrapped up into a useful tool this quickly. It means that tools are here, great job, industry!

@Pat that was quick too! ;)

By: Dave

Dave — Mon, 03 May 2010 23:05:06 +0000

Very cool – I wonder if anyone has implemented hardiff yet?
It would be useful even if the output were simply text/json, but I can dream about a waterfall chart that compares two runs – maybe like the ghost driver some racing games show overlayed on your current lap.

By: Wim Leers

Wim Leers — Mon, 03 May 2010 22:30:01 +0000

Excellent remark by Jennifer Showe. And thanks for that link to Sergey Chernyshev’s blog post, Steve. I will definitely try to use this in my master thesis!

By: Patrick Meenan

Patrick Meenan — Mon, 03 May 2010 17:15:44 +0000

FYI, I just pushed the code to support exporting HAR files from WebPagetest as well. It’s available as a link in the top-right corner of the summary results as well as on the waterfall page.

Sadly WebPagetest doesn’t keep the full responses around (just the headers) so PageSpeed can’t do very much with it.

Since I’ll be working on pagetest anyway to integrate with the PageSpeed libraries I’ll see if I can add HAR export capabilities there as well which would allow for full responses to be included.

Where things could get really interesting will be when I can get time to add HAR import capabilities to WebPagetest.

By: Steve Souders

Steve Souders — Mon, 03 May 2010 17:14:37 +0000

@Jacob: For realistic results, you need to run a headless browser to generate a HAR file. This is possible, but goes beyond a simple commandline tool. Sergey most recently talked about how he does this with xvfb: http://www.sergeychernyshev.com/blog/automating-yslow-and-pagespeed-using-xvfb/

By: Jacob Rask

Jacob Rask — Mon, 03 May 2010 12:52:09 +0000

Are there any commandline tools (Linux compatible preferably) to generate HAR files? It would be nice to be able to run a cronjob and check a site every day and generate charts from that, similar to Pingdom and other services.

By: steve

steve — Sun, 02 May 2010 23:49:54 +0000

Thanks for this article. List time seen some of those plugins mentioned. Added a few more to my testing suite, thank you

By: Steve Souders

Steve Souders — Sun, 02 May 2010 18:40:14 +0000

@Jennifer: Awesome, thoughtful comment. We want both: As an industry, we need a common yardstick so we get apples-to-apples comparison. But we also want innovation. My thought is there would be a common formula for a canonical performance “score”, but tools could go beyond that to dig into other areas. To your other point about raw data – HAR facilitates this by decoupling the gathering of data from the analysis. With HAR, analysis doesn’t have to occur live in the browser – it can be done later (even retroactively) using the HAR file.