Sitespeed: Do images require width and height attributes?

[cyberlicious]

Currently working on a sitespeed issue, and was wondering if not having width and height for images actually do cause a problem.  We simply Photoshop the resolution we require for the image and add it to the page as is.  I though this would actually speed it up, but I am getting from www.gtmetrix.com that we should have them.

What's your experience?  Thanks!

[ThompsonPaul]

The main reason PageSpeed and YSlow recommend including width and height for images is as much the perception of page speed as the actual load time, Ben.

When you include the image dimensions, the browser can draw out the "containers" that will hold the images, reserving the space for them while they download. The browser can then go on the paint the rest of the pages CSS and objects around those "containers" without having to go back and redraw the whole page once the images have downloaded and their sizes are then known.

This gives the user the illusion of a much faster, cleaner page load, and hence the impression of a faster website.

Does that make sense?

Paul

[Edited to add: You should still keep doing what you're doing to produce "size-as" images for your pages. You don't want to be resizing images with the html dimensions, just reporting in html the actual size of the image]

[cyberlicious]

Perfect-O!  I completely get it now.  Thanks Paul.  You da man!

I thought it would be faster as in my mind it was more to read, but now that I understand the loading, I get it.  Guess I need to start researching how a website loads.  Have any resources I can read, to up my experience with this?

I've been in development but on an application side not website side.

[mememax]

as Paul correctly said, if your purpose is to improve the page speed just be sure that you're not resizing the images with css/html but that you're uploading the images in that dimensions.

An image of 10241024 resized to 100100 still weights as an 1024 image so my recommendation is to resize all those images to the desired dimensions, moreover if you can use an external cdn you'll save bandwith and have those images loading outside your website. That will help reducing the loadtime of the page.

[cyberlicious]

Yes, thank you.  We size them all to what we want on the site so we are good there.  Just got done doing it, and it did make a difference.  Thanks guys!

[mememax]

you're welcome, hope your site will be speeding up a lot!!!

[ThompsonPaul]

Just came across a terrific resource that reminded me you'd asked about further reading, Ben.

Check out BrowserDiet for a huge collection of resources about tuning front-end performance of websites. (You'll see #6 talks about exactly your original question)

I can also recommend reading Steve Souder's two books - High Performance Websites and Even Faster Websites - both from O'Reilly. Souders is pretty much the leading specialist in this area. He's the creator of YSlow, one of the primary tools for measuring/analyzing site speed, and is now Head Performance Engineer at Google. His website is SteveSouders.com

That'll be more than enough to get you started. Lemme know if you're still hungry for more!

Paul

P.S. The report details from tests at webpagetest.org can also teach you a huge amount, and there's a forum there run by Patrick Meenan (who built webpagetest) which is just excellent. Patrick frequently answers questions personally.

[cyberlicious]

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