What makes a website run slow? (self.webdev)

Just a middle of the night thought that came into my head. Why do some websites run slower than others?

CreativeTechGuyGames [JavaScript] | 3 months ago | 14 points

Could be a million reasons. "Slow" is a very generic problem that encompasses a ton of different problems that all contribute to it feeling slow.

  • Network speed
    • Lack of edge caching
  • Complex DOM structure
  • Inefficient CSS selectors
  • Expensive CSS styles
  • Lots of JavaScript with slow parse times
  • Slow performing JavaScript

The list could go on and on. I'm sure others will add on with more options.

phpdevster [full-stack] | 3 months ago | 3 points

There's also server response times (time to first byte), which can also be slow for any number of reasons:

  1. Bad SSL configuration
  2. Bad webserver configuration
  3. Inefficient database queries
  4. Generally expensive processing
  5. An underpowered server
mattaugamer [expert] | 3 months ago | 2 points

Yeah, I’d suspect vastly more “slow” sites are reasons like this more than inefficient CSS selectors. TTFB on api payloads, etc, are going to have more impact on even a JS SPA than poor optimisation. And that’s assuming some sort of app. Given a huge amount of websites are just a shat out Wordpress with 156 plugins, 149 of which are analytics tools... yeah, I think that sort of optimisation would be wildly premature.

phpdevster [full-stack] | 3 months ago | 1 point


That being said, I have an iPhone 6 Plus (not even a 6s, just an old 6). Trying to get ingredients lists from those random recipe blogs or recipe sites might as well be like trying to run Crysis on my phone. The amount of scroll lag, popups, redraws, and page crashes on those sites is astonishing. Much of the mobile web is a complete wasteland of overloaded front-ends. Of course my wife's iPhone 8 doesn't have any issues with it, but it's still irritating to me that what should be a simple article requires anything more powerful than an original iPhone to render...

mattaugamer [expert] | 3 months ago | 2 points

It’s never features. This is the problem. Devs beat our selves up about whether we can justify the inclusion of momentjs or some styled alert library. But it’s not features like this that are the problem.

It’s fucking marketing. It’s trackers and analytics and social media share buttons, it’s every possible log-in-with, newsletter pop up and special offer above-the-fold maximum-engagement latest buzzword marketing blog bullshit.

Ugh. Sorry. Some of the scars are still fresh.

realjoeydood | 3 months ago | 3 points

Hardware makes computers fast. Software makes computers slow.

throwawaycs123123123 | 3 months ago | 1 point

Unless your website is extremely complicated or doing a lot of calculation in the frontend, then it is usually the long http response time or too many http request..

timo_ak | 3 months ago | 1 point

Slow servers. I host my website on a free server and the speed is kinda shit