I would like to improve rendering performance of http://www.camping.info/campinplaetze. Running a test on WebPageTest.org I see in the waterfall chart that for images loaded from http://images-camping.info, Chrome initially opens only three connections, and only at the 2 second marks opens another three. That's why the first 6 images are loaded consecutively, all on the third open connection as seen in the connection view:

Resource view Connection view

I would like Chrome to open the six concurrent connections to images-camping.info around the 1 second mark so that it could download more images in parallel which I assume would make rendering the page faster.

Does anyone know of a way to do that?

  • 2
    Running HTTP/2 will probably give you an even better pipeline for serving multiple resources. Feb 23, 2016 at 12:18
  • It's probably time to turn this on in our NGINX server...
    – Oliver
    Feb 23, 2016 at 14:02

3 Answers 3


Short Answer - every browser has a specific limit to open parallel connections. In the case of Chrome this limit is 10.

If I was there, I would do only two things:

  1. Optimize images - If you're using png files, then I suggest to use tinypng.com, because it compresses images well, compared to Google PageSpeed module.

  2. Serve Images from CDN - Use Amazon Cloudfront CDN to serve images, because image URL begin with Amazon Cloudfront URL, so you don't need to use second domain, here is an example of how they serve images with their domain name. CDN helps in many ways.

  • From you link I can see that Chrome uses only up to 10 parallel connections - this explains my observations perfectly. Thanks also for the other tips.
    – Oliver
    Feb 22, 2016 at 18:43

You can have several subdomains (CNAMEs) and load some resources via them, eg:

  • css.domain.com
  • js.domain.com

or, better, assets1, assets2 etc. They all point to the same server, but in your page sources you use different subdomains to trick the browser around


I can't give you a fullfit answer because I am not sure if you can tell Chrome how to load your page, but least you can do is to optimize your website.

  1. Starting with Expire Headers, make sure they are working correctly, not just for images but for basically everything.

  2. Optimize the pictures in your website, I believe you have done that but if you haven't yet, then use an online convertor like tinypng.com or other to compress your images.

  3. Use .gzip compression for src files and minify them.

There are sure more things to dig into performance optimization but I think you should consider to start with these three basic things and if they help you I can give you further advices.

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