Lossy vs. Lossless Image Compression

10 Jan, 2024

Image compression is a popular method to reduce the total file size of your images. When you have compressed images, it will help you reduce the loading time and increase the overall performance of your website.

We have two image compression methods; one is lossy compression, and another is lossless compression. Both of them will reduce image size significantly. Still, there are differences in their way of compressing and the output of the compressed image.

This post will explain the difference between lossy compression and lossless compression. We will also see why image compression is a critical practice to enhance the user experience of your websites.

And I will then provide a list of tools to help you compress your images strategically and effectively to use on your WordPress sites.

What Are the Benefits of Compressing Images?

Suppose you use large images on your website. In that case, it will negatively slow down your website performance, directly affecting your SEO efforts and user experience.

Large-sized images will take so long to load. Unfortunately, this will make the page inaccessible or unresponsive. Your visitors will see an endless loading animation on your website title bar, and they will leave your site immediately.

You see the problem here, don’t you? So this is the reason you need to optimize the images you upload to your website.

You can optimize those images by resizing the resolution or compressing the file data. Both of these methods will help you reduce the file size of your photos, and your website will load faster.

Google found that 45% of visitors won’t return to a website if their first visit was unpleasant. Google also publicly confirmed that your page speed would contribute to your search engine ranking. And it is very crucial.

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Moreover, slow page performance will affect your overall conversion rate as well. A faster page load will increase the revenue of your website.

Smaller image sizes will also help you with your hosting subscription. Smaller images will always use less disk space than large images. So you will have more storage space for hosting other content.

It will help you backup your website faster as your overall file sizes are lower now. So the backup and restoration process will be faster. It’s even more crucial when you’re restoring a large site at once.

So I have told you there are two compression methods. Now let us see which compression method will best fit your WordPress website.

We will now look at the differences between the lossy and lossless compression techniques.

Lossy Image Compression Decreases File Size

With the Lossy image compression process, the processor will remove some of the data from your image file. And that will help to reduce the overall size of the file.

This process is unreversible, which means once you compress, the data removed from the file will be permanent, and there is no way to restore them.

The Discrete Cosine Transform, Fractal Compression, and Transform Encryption are examples of algorithms used for lossy compression.

These lossy compression algorithms will reduce the file size significantly, but there is a trade-off. The method will also degrade the image quality. That is why it is always better to take a backup file before compression.

The JPEG file format is an excellent example of lossy image compression. The JPEG file format is most suitable for pictures and photographs that are not transparent.

JPEG formatted images are great for a website that needs faster loading time. You can configure the compression ratio while keeping the quality under your control.

When you upload JPEG files to your WordPress Media Library, WordPress will automatically compress images up to 82% by default. You can increase or decrease the value or disable it altogether. I will show you how you can do that later in this blog post.

Lossless Image Compression Prioritizes Quality Over Size

Unlike Lossy compression, Lossless compression won’t reduce image quality. Do you know why?

When we compress using the lossless compression method, the process only removes additional and non-essential data automatically added by the system used to take the photo.

It can be your mobile phone, laptop, or camera; this compression method will only remove non-essential data.

But the trade-off for this method is that you then can’t see a significant data reduction in the image file size. So this compression method won’t help you save data storage space much.

Arithmetic Coding, Huffman Coding, and Run Length Encoding are standard lossless compression algorithms.

The lossless compression technique nicely compresses text-heavy images and pictures with transparent backgrounds. That means you can use lossless compression to compress image types such as .RAW, .BMP, .GIF, and .PNG.

So, lossless compression is the best compression method for images that stay high quality, such as computer-generated graphics.

Lossy CompressionLossless Compression
It eliminates the data that is not noticeableIt does not eliminate the data that is not noticeable
A file does not restore or rebuild in its original formIt can restore a file in its original form
Data quality is compromisedData quality is not compromised
Data size decreasesData size won’t decrease
It is used in images, audio, videoIt is used in text, images, sound
It has more data-holding capacityIt has less data-holding capacity
It is called irreversible compressionIt is called reversible compression

What Is the Best Way to Compress Images? Lossy or Lossless?

That’s a question that is not easy to answer. I believe that the correct answer will depend on your requirements.

Suppose you are running an e-commerce website, blog, or portfolio website. So, you may find lossy compression will be more beneficial as it offers a significant file size reduction.

And when you use small file sizes, that will help the website perform better. And this, in return, will create a better user experience and will improve your SEO ranking.

Are you using a photography website? It would be better to use lossless compression because this data compression method will prioritize quality over reducing the file size.

And that means you can showcase your photography skills in more detail. Your visitors will feel the granular level of detail that your photography skills deserve.

You can use both lossy and lossless methods on the same website pages depending on the purpose of the individual pages.

For example, you can optimize your e-commerce site with lossy compression for your thumbnails and preview images, which will help you reduce the load time.

However, for the product images, you should go for the lossless compression method to preserve the quality so your visitors can see the product detail from a much better viewpoint.

Please note that you can use this tip on almost any type of website.

Lossy Image Compression Within WordPress

Suppose you use WordPress as the CMS and decide to use lossy compression. In that case, WordPress can compress those images automatically for you. If you want to adjust the compression ratio, you can modify that by using a single line of code.

You can use the following filter to let WordPress automatically compress by the specified ratio.

WordPress will compress your images to 70% of their original quality as specified in the below code snippet. You can add this code into the function.php file of your active WordPress theme.

add_filter( 'jpeg_quality', create_function( '', 'return 70;' ) );

This filter won’t impact the images you have already uploaded to your WordPress. You need to regenerate those images you have already uploaded using free plugins such as Regenerate Thumbnails.

Suppose you wish to disable WordPress automatic image compression. In that case, you need to add the following filter to your active themes function.php file.

add_filter( 'jpeg_quality', create_function( '', 'return 100;' ) );

This code and the above code are indeed the same. We just increased the ratio value from 70% to 100%.

Suppose you don’t have the technical knowledge to edit such configuration files. In that case, I strongly recommend you use the offsite image compression method. That will be very easy to execute, and you don’t need to install any WordPress plugins.

Below is more information about that.

The Best Way to Compress Images for WordPress

Now I will show you the best way to compress images for your WordPress website. This is the method that I am following for my websites.

With this method, we will upload the images to the TinyPNG website. This website will help us to compress images. It will currently support JPEG and PNG files, and they recently added support for WEBP file types.

Once you upload your uncompressed images to this website, you will instantly see a compressed version.

TinyPNG Compressed Images

Then you can download that file and upload that compressed file to your WordPress media library directly.

Remember that, as I said earlier, this method will only help us to compress new images. And those images that we already uploaded won’t be compressed.

Suppose you are a WordPress plugin addict and you don’t like this method that I explained above. In that case, you can use various plugins like Imagify, Smush, ShortPixel. TinyPNG will also have its WordPress plugin.


Both lossy and lossless image compression methods have their advantages and disadvantages. I recommend picking the best image compression method to suit your website’s needs.

Or you can also use both compression methods depending on the purpose of the individual pages on your WordPress website.

Please remember that compressing and optimizing images that you upload to your WordPress website will have various benefits.

Compressed images will help your website load faster and improve your SEO and PageSpeed score. You will enjoy the benefit of compressed images when you try to backup and restore your website.

I hope this blog post will help you understand the difference between lossy and lossless compression. Let me know which one works best for your site.

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Jafar Muhammed

Jafar Muhammed has 10+ years of experience in WordPress, web hosting, domain names, DNS, CDN, server administration, etc. He is an open web advocate. He is the CEO of Rovity, the fastest-growing premium shared hosting startup in India.