Save the Internet from WordPress speed abuse.
PagePipe reviews all of the files in a client’s image library to see how optimized they are. We install a plugin that indicates the “space used” by each file. This is the page weight expressed in “k” (kilobytes).
Media File Sizes Plugin
Displays file sizes next to media items in library. (For image files, also displays total size of all generated sizes.)
Images are traditionally half of all page weight – code and other assets make up the rest. Optimizing images can make a big difference in load time. But it’s just the first thing to try.
WP Smush plugin has a fault or myth. Their advertising encourages the false sense you’re automating everything possible to optimize images. In reality, WP Smush does very little to help. Their goal is to influence you to upgrade to the Pro (paid) version. The free version perhaps produces a best-case 10% improvement for jpeg images. This is not enough to make a significant difference in page load time. It’s one of the least beneficial of image optimization plugins we’ve benchmark tested. Yet the most popular. Go figure. Over a half million active installs!
The best-case scenario is always optimizing your images by-hand – meaning using an image-processing program or application. But for those with hundreds or thousands of images to optimize, we can understand why you would want to automate image optimization. But it will always be second best.
Remember: WordPress recently changed automated image optimization from a quality setting of 90 to 83. This makes images comply with the standards set by WebPagetest.org. That means no red flags go up for images when you speed test WordPress. But, Christian Nelson, has informed us that in his tests WordPress automated optimization is not applied to the “original” image – only to the stored medium and thumbnail images. From our experience, images that are cropped or edited using WordPress image library functions will be optimized. Ironically, in some cases, this produces a larger page weight. This can undo your by-hand optimization. So double check.
So if WordPress is doing some image optimization work already, what do you need to do? You need to make sure the physical dimensions of the file (height and width) are reduced to their proper size. That will prevent waste. Note: Setting the image resolution to 72ppi makes no difference in speed, page weight, or image quality. For a demonstration and explanation of this go to: http://daraskolnick.com/image-dpi-web/ Another tip of the hat to Christian Nelson for this informative link.
A good failsafe is installing Imsanity plugin. Imsanity automatically reduces the size of images that are larger than the specified maximum and replaces the original with one of a more “sane” size. Site contributors don’t need to concern themselves with manually scaling images and can upload them directly from their camera or phone.
The resolution of modern cameras is larger than necessary for typical web display. The average computer screen is not big enough to display an 8 megapixel camera-phone image at full resolution. WordPress does a good job of creating scaled-down copies which can be used, however the original images are permanently stored, taking up disk quota and, if used on a page, create a poor viewer experience.
Imsanity plugin is designed for sites where high-resolution images are not necessary – or site contributors do not want (or understand how) to deal with scaling images. This plugin should not be used on sites for which original, high-resolution images must be stored since it overwrites the originals.
So in a nutshell, Imsanity allows you to set maximum physical dimensions and also a Jpeg image quality setting. We use a setting of 70. You can also bulk resize all of the existing images in your media library.
Usually web designers optimize images before uploading. No or negligible improvement are made by WP Smush plugin after that.
People don’t understand lossless image compression means fat. You want lossy images (skinny). Lossy images are visually lossless. That means they weigh a tenth but look the same to the human eye. WP Smush doesn’t do lossy optimization – period. They think fat is better. It isn’t.
It’s lame because WP Smush doesn’t 1) resize image dimensions and 2) it has fixed, lossless, default image compression settings. If you upload an oversize (dimensions) image, it remains the same size. Still too large. Gains during WP Smush compression (file size) are typically only 1% or 2% for Jpegs and potentially more around 12% for PNGs. These are insignificant in most cases compared to real potential savings.
Additionally, thumbnail and medium size images are automatically being produced and stored by WordPress on your server space whether you need them or not. (This can be switched off with a simple dashboard trick. Settings > Media > thumbnail size = make both dimensions zero. Same for medium size. Make them zero. No more small image production).
WP Smush attempts compressing these unused images also and includes the “savings” in its stats. This isn’t real savings since these images aren’t necessarily used on your site. That’s what it means when it gives “all sizes” savings numbers. Fluffy.
Bottomline: There are no big gains made with image optimization with WP Smush plugin.
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Serious WordPress Speed Strategy for Business