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How To Optimize Images For WordPress, A Complete Guide

January 26, 2015
How To Optimize Images For WordPress, A Complete Guide

People on the web don’t have much time to consume data – because there’s so much of the latter. There’s so much data that we simply don’t have the time to read it all! As a content curator for the modern web, your task is to maximize throughput. The more you express with lesser words, the better you are at your job.

Why are Images (so very) Important?

There are many, many reasons why your would (and should) use images in your posts and articles:

  • Images serve as visual stimuli for a call-to-action (CTA). A CTA can be any task you want your visitor to perform. Common CTAs include subscribing to your newsletter, sharing your article over social media or buying your product.
  • Images enhance the connection the writer seeks to establish with the reader.
  • Images convey more through less.

It is therefore, quintessentially important that we use the right images in our presentations (blog post, informal report, actual PowerPoint presentation etc.) in order to leave a mark in the reader mind!

But wait! There’s a problem!

Images take up around 63% of the bandwidth used by modern websites, so it is increasingly important that they are properly optimized for speed.

A one second delay in page load times could reduce conversion rates by 7%

We’ve established that people have a short attention span (one of the downsides of the modern content production rate). Even if you use the right images, if they do not load within the acceptable timeframe, the interest is lost.

The majority of sites have the same problem – they use excellent images, but the way the image is served to the visitor is poor. Large size, poor optimization, incorrect format, unnecessarily large dimensions (sizes), unresponsive images and careless SEO errors, are some of the most common problems the modern web faces. In today’s article, we’re going to give you 10 easy image optimization tips you can use to avoid these issues.

1. Resize Images with Large Dimensions

“Extra Fries” aren’t always good

This one’s a classic. Suppose you need a 150×150 pixel photo in your site’s “Team” page. Usually, you’ll use a 5MP headshot, edit it a bit and finally upload it.

Did you spot the problem? Some folks directly upload the actual 5MP image! The WordPress theme will load the entire 5MP image (that’s 5 x 10^6 pixels) and ask the browser to shrink it to the required dimension of 150x150px. In essence, the browser displays only 0.0045% of the original image!

You end up wasting both your and your visitor’s bandwidth (even if you’re serving the image via a Content Delivery Network like Stackpath CDN), consuming more hard disk space and increasing the load time. None of the features are something you’d want in your site.

Always resize (and by resize I mean downsize) the image to the required dimensions and then upload it!

You don’t need fancy software to do this – there are free online tools like you can use to quickly resize and optimize your images. Just upload and tweak your photo settings. When you’re done download your optimized image to use on your site. They also offer a quick Image Compressor if you just want to cut down on file size.

Helpful Tools:

  • IrfanView is an excellent freeware to batch-resize your images with advanced options like optimization, watermark and borders.
  • ImageMagick is an advanced open-source tool which can be used in a variety of programming languages and operating systems. You can write your own app or simply use it via the command line.
  • ImageOptim (Mac) allows you to drag whole folders and quickly optimize multiple images.
  • TinyPNG is an online image compression tool with an API.

2. Use the Correct Image Format


The format used for the image plays a vital role. As a general rule of thumb, use PNG for vector graphics and computer-generated images such as clip art etc. Use JPEG for photographs or images with a variety of colours. For a detailed explanation, check out this awesome StackOverflow answer.

3. Use Progressive JPEGs

Baseline (Normal) JPG versus Progressive JPG

Baseline (Normal) JPG versus Progressive JPG

For the common man, JPEGs are of two types – Baseline and Progressive. Visually, both are same. The difference lies in the way they’re loaded:

  • Baseline JPEG has only one layer – containing the whole image. When requested, the entire image is loaded at one go.
  • Progressive JPEGs compose the image with multiple layers. A Progressive JPEG image is loaded layer by layer, which gradually increases in quality, ultimately giving you a lossless view.
IrfanView Supports Batch Conversion with Progressive JPEG

IrfanView Supports Batch Conversion with Progressive JPEG

All major image resizers allow you to save images as Progressive JPEG.

4. Enable Lazy Load

Lazy-Loading is an excellent resource saving technique where an image is loaded only when the visitor scrolls down to the view-frame of the image. Consider an article – “15 of the Most Fuel-Efficient Cars in 2014”. Naturally, this article will contain at least 15 images. And no matter the height of the display device – monitor, tablet, or smartphone, you cannot fit all 15 images in the view-frame. You must scroll down to view all the images.

With Lazy Loading enabled, images will be loaded only when a visitor is in the vicinity of the image. In other terms, the images start to load just when you scroll down to view it. The first few images, however, are loaded instantaneously, since you’re already in the view-frame. Lazy Loading saves bandwidth at both ends and improves load time! You can use Lazy Loading in WordPress with the BJ Lazy Load Plugin.

5. Add a CDN


Using a Content Delivery Network (CDN) will serve the image from a server which is physically closest to the visitor’s location. If a visitor from India requests an image, and the CDN has a POP (point of presence, or simply a server) in Tokyo and New York, the image will be served from the server located in Tokyo.

When you have considerable traffic, you should setup a CDN with WordPress in order to lower your load time and gain overall performance.

Here at WPExplorer, we use Cloudflare, and we have an added list of recommended free CDN services you might want to checkout. But setting up a CDN yourself can be complicated, which is where a plugin can come in handy.

Publitio Offload Media

Publitio Offload Media Plugin

A great option is the Publitio Offload Media plugin which allows you to store your media files on the Publitio cloud-based media manager. With the plugin installed you can easily move your entire media library off of your servers, and even optimize image and video quality when you do. Once moved, images are swiftly served from the Publitio CDN. This frees up tons of server space and can really speed up your site (especially if you’re on a budget hosting plan with limited space). There’s even a simple Sync Now button to automatically add new media to the cloud as you edit new posts. And premium Publitio plans include extra features for custom CNAMEs, multiple watermarks and even video encryption.

6. Declare the ‘alt’ Attribute

The ‘alt’ attribute describes the image for the search engine. The text you enter in this field will be displayed to the user in case the image cannot be loaded. A lot of people tend to leave these fields blank. This is very detrimental for SEO, and you lose out on traffic. You should always try to include your site’s keywords in your images’ alt tag.

7. Optimize an Compress Images


Optimized images are 40% lighter than normal images. This improves load-time and saves bandwidth. From Freddy’s list of the Best WordPress Image Optimization Plugins, we would recommend to optimize your images. is also a great online option for compressing images in a jiffy. We use it all the time here at WPExplorer to optimize featured images before uploading them to posts and theme demos.

8. Responsive Images

Responsive Web Design is here

Responsive Web Design is here

Even if your site is responsive, doesn’t mean your images are. That means the header image you use for a 22″ desktop screen is also served to a 5″ iPhone. When you upload an image, WordPress resizes it into multiple versions – Thumbnail, Medium, Full Size, etc. This can be changed by the developer. A well coded theme will serve the “Medium” sized version of the image, thereby saving bandwidth.

The Picturefill.WP plugin will replace image tags with a new <picture> element that would serve different images based on media queries. It’s fairly experimental (that means there are bugs) and shouldn’t be used on a live site.

9. Image Captions

Captions aren’t always necessary, although in some cases, it is required – such as screenshots in a tutorial. Captioning images helps readers understand the topic better, while boosting your SEO.

10. Image Filename

Think about the filename from a search engine’s point of view. Use the same text as you would in the ‘title’ tag of the image. Also, try to include your keywords that are most relevant to your site.


Image SEO is critically important for any website – old or new. Folks who implement image SEO properly (it can be quite mundane at times), stand to gain a significant amount of organic traffic (the best kind of traffic) in the long run.

Have an awesome optimization technique? Fire away!

Article by Sourav guest author
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  1. Daniel Petre

    Jpegmini for Mac is awesome at reducing jpegs.

  2. john cartlon

    Hi Sourav, Great post. Here are the best image optimization plugins to speed up WordPress site:

    EWWW Image Optimizer
    CW Image Optimizer
    PB Responsive Images and many more…

    – John

    • Traian

      I may suggest you adding ShortPixel Image Optimizer too 😉

      • AJ Clarke

        Yes, ShortPixel is another great alternative! For those interested you can check out the plugin here.

  3. Angus McKinnon

    Thanks Sourav. Lots of good advice. I had forgotten about progressive jpegs. Only thing I would add is use of sprites for recurring images like in navigation or social sharing.

  4. Mr Sumit

    Thanks very informative one, But I have few doubts. Is CDN Network and Cloud Based Solutions are helpful or not ??

    • AJ Clarke

      Definitely as long as you pick a high quality service 😉

  5. Emily

    Very helpful for me to start writing. Thank you very much

  6. Jacob

    Very useful articles, thanks a lot. It’s also a good idea to use the CSS sprite method to combine multiple images into a single one, then compress this image with standalone programs like photoshop or online image optimizers.

  7. Eric

    Awesome post! I can recommend Optimus to optimize your images in WordPress:

    • Kyla

      Hey that looks like another great online tool! And compressing the jpegs is even free 😉

  8. Apps Addict

    There are number of free tools available in the shape of wordpress plugins offering better optimizations for them.

  9. samantha

    I would love to know how to optimise my images and get some guidance around it, is this something you would offer as a consultancy basis please?

    • Kyla

      At this time we don’t offer any custom services or work – but a good place to start is just smushing/compressing images yourself and using some of the other tips in the guide.

  10. Jan

    Do anybody know of a plugin or service, where you upload that large image, and the image is automatically cropped, resized etc. in specified formats and placed in the media library?

    I got quite a lot of clients, who don’t know how to do this right and just upload the large image without thinking of the above mentioned problems – and they don’t want to spend time learning this or spend money on someone to get it done right…

    • AJ Clarke

      Your WordPress theme should already do this for you so when a client uplaods the image to the media library all the cropping is done for them. For example in our Total theme we have a whole Image Sizes panel where you can define your image sizes and the theme will dynamically create these image sizes.

  11. neo

    useful content, i use caesium desktop software

  12. deepika singh

    hello, Sourav
    Thank you so much, you wrote the topic on this blog, I needed such a topic… Because my website also has some similar problems … I don’t know how to optimize the image … You told this topic very well and I will definitely follow your mentioned methods.

  13. MI

    I didnt know that caption also boost SEO. Thanks.

  14. Barun Chandra

    Valuable information regarding image optimization. Especially for bloggers who’s blog holds a lot of images. Since now I will keep an account of some of these points. Anyway, great article. Keep it up.

  15. Sumon Mondol

    I’m starting my own blog but I’m having a tough to Image optimize in WordPress.
    I don’t know how to optimize the image, Thanks for sharing these blogs and I’m looking for
    something unique. Next time I follow this carefully.

  16. Timothy Maloy

    Thanks for your sharing, the article was very helpful for me. I often learn how to optimize images for WordPress on online courses schools with many different tutorials.

  17. Lara Jones

    In wordpress we make websites very easily same now on page SEO also very easily done. image SEO now in trending, and your blog beautiful describe how we can Image SEO for our websites.

  18. Lisa

    PNGGauntlet is the best tool I’ve ever used to compress PNG. It is a fully free software application, which runs images through numerous algorithms and offers a wild, absolutely lossless compression ratio.

  19. Jennifer S Ho

    This is very helpful article! Your suggested solution of imageresizer solved my issue of images not uploading. Thank you! I had tried several image compressor websites, but they all cost money over a certain limit and did not adequately compress my images.

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