How to Reduce Image File Size & Keep Quality

Have you ever had one of those photos you wanted to share or upload, only to find out there was a restriction on file size? In this tutorial, I’ll show how to use free online image compression services to reduce the image file size without sacrificing image quality. And for good measure, I’ll discuss some desktop applications and ChatGPT as well.

Part of the photo file size problem is that the digital cameras on our smartphones improving. I saw an ad for the Galaxy S23 Ultra boasting a 200MP camera. This means the original photo can be huge in pixels and file size (Megabytes).

Recently, one reader wanted to upload her images to an online photo contest, but the website restricted the file size to 5MB per image. She wanted to know how to reduce the photo file size so she could submit her entries. A similar issue happens when people want to use suggested image sizes to upload to social media sites.

How to Reduce Image File Size

In remembering my reader’s question, there are several ways to tackle the issue. These fall into two buckets: image resizing or adjusting image quality.

  1. Reduce the image dimensions or pixel density. For example, if the original image was 4000 pixels (px) by 2000 px, you could reduce it to 2000 px by 1000 px. Many image editing programs like SnagIt, Affinity Photo, Microsoft Paint, or Microsoft Photos can restrict the image by percentages or the number of pixels.
  2. Use a Templated Service such as the Adobe Express free tool that Adobe Photoshop powers. This service works with JPG and PNG file types. It lets you apply predefined templates to your uploaded image. Think of Adobe Express as a quick image resizer that works with: Instagram, Facebook, Twitter, YouTube, Pinterest, LinkedIn, and Snapchat. They also provide options for defined aspect ratios for widescreen, landscape, presentation slides, and so on.
  3. Photo-cropping works well if you can remove non-relevant areas from your image. However, always make a copy of your original picture. Cropping an image can impact dimensions and aspect ratios.
  4. Use an image compression routine to remove extra data, including EXIF data.

Certainly, many software packages can do the above steps and offer many resolution options. However, they can come with a steep learning curve or expense.

However, you can use one of the free image compression websites. The results will be a much smaller photo image file but with the same image dimensions. This process is useful if you need to reduce Microsoft Word file sizes that contain images.

Image Compression Services

There are many of these services to test, so I concentrated on a few. These included both online services where you needed to upload a file as well as desktop applications.

My Testing Criteria

When looking at these services, I had some requirements in mind.

  1. Cost – I was looking for free services
  2. Ease of use
  3. Privacy and ownership (what happens to the photo)
  4. Overall Features
  5. Ample file upload size
  6. Image file formats – I was concentrating on JPG.

In many cases, this info was stated on the website or instructions. However, there were some services that didn’t address these issues.

How I Tested the Services

I bought a high-quality photo (JPEG) that weighed in at 9629 KB or 9.2 MB to test the image optimization services. My math was based on the original file size and the resulting file size. In some cases, online services showed different values.

This is also a reminder that you shouldn’t rename your newly compressed images to the same name as your original file. Always keep your original pictures, as you may want to test various services. Another reason is some file formats, such as JPG, can suffer from pixelation if you try to enlarge them.

Initial test photo.
Test Photo © Patryk Kosmider

The test photograph was 4500 px X 3000 px. Once I finished testing, I opened Snagit and Affinity Photo to see if I could notice visual differences between the files. These are two commercial programs I use. From my perspective, the original and compressed images looked the same. I didn’t see any washed-out colors. Some services had a preview function that allowed me to compare “before” and “after” images.

JPEG.IO

JPEGIO image and results.
JPEG.IO Results

What I liked about JPEG.IO was the simple design. Although I was focusing on JPG images, I was surprised to see many supported image file formats, including WebP. It also allows you to import images from 3rd party storage services like Dropbox, Google Drive, and Box. Although you can’t see the full image until you download the file, I could see a thumbnail image when I hovered over the button or clicked Download File.

What I disliked was that there was very little information about the site and service. I could see a lone pop-up dialog, which told me the service used Kraken.io proprietary technology.

Kraken.IO is well-known for image compression and tools. I’ve used their paid services in the past with great success to optimize images for this website. From the domain registration, I thought the same company might own JPEG.IO. However, I never got a response to my email inquiry.

The service reduced the picture from 9.6 MB to 3.56 MB (37% of the original). The version looked just as good as the original.

Final Image size: 3561 KB / 37% of original.

OPTIMIZILLA

Optimizilla picture and results.
Optimizilla Results at 83 Quality score

Optmizilla didn’t seem as polished, but I learned it is feature-rich. They clearly state the JPG or PNG files you upload will be deleted in 1 hour. Two items stood out. The first was they offered 14 different language options other than English, which I thought was a nice touch.

Secondly, they allowed me to use a slider to adjust the image quality. This is something you might see in desktop software. I didn’t see this feature always offered. For the test, I kept the default setting. I could’ve dropped down the Quality slider setting to get even more file size reduction.

The output examples of the before and after images weren’t as large as other services and contained an inset. When the initial thumbnail loads, I’m guessing it’s using the image center. You can click the image and locate a more important part of the photo for comparison.

One item that may confuse you is the advertisements. I don’t have a problem with ads, and I know webmasters don’t always have control. However, the site had some that appeared to compete with the service, with START and DOWNLOAD buttons.

The service reduced the file size the most, bringing it down to 20.1% of the original size. As with the other services, the compressed image looked fine to me.

Final Image size: 1931 KB / 20% of original.

COMPRESSOR.IO

Compressor.io file results.
Compressor.IO Results

Compressor.IO is a personal project of front-end developer Stephane Lyver and uses open-source software such as OptiPNG, JPEGOptim, etc. The service did an impressive job at image compression. The resulting photo was reduced to 24% of the original size. According to the site, it’s possible to get a 90% file reduction. It can optimize JPEG, PNG, SVG, GIF, and WebP.

The service allows 3 options for compression: Lossy, Lossless, and Custom. If you drill down into the custom options, you see additional options, such as resizing the image and fine-tuning the image quality. However, these options are not available on the free version.

Pad options panel for Compressor.io
Paid options

Final Image size: 1326 KB / 13.7% of original.

ChatGPT 4 Experiment

With all the AI improvements, I was curious if any of the services could assist. I do have a ChatGPT Plus account which now includes DALL-E. But first, I wanted to verify.

ChatGPT responding to my file size question.

The reply looked promising, but since there wasn’t any image options as with the other services, I asked for clarification. Again, I was pleased with the response.

ChatGPT telling me to upload image file.

To keep my testing straight, I used the same image as with all the other services. I even indicated it was a stock image I bought in case there was some licensing issue. And then things went downhill. The first issue was there were too many requests being processed at the same time.

Things looked a bit better on the second attempt to compress the image. The system responded with:

The compression has been completed successfully. The original image size was 810 KB, and the compressed image size is now approximately 681 KB. The dimensions have been preserved.

Immediately, I noticed the original file size was wrong. The original test photo was over 9MB so I’m not sure why ChatGPT seemed to think it was 810 KB. But that wasn’t the only difference as when I asked for dimensions, it indicated the original photo was 2048 x 1365 pixels. It was 4500 x 3000 pixels.

At this point, I gave up since the output wasn’t what I asked. I’m certain in the future these issues will get worked out, but for the time being, I wouldn’t use to reduce image file size.

Desktop Applications

Some people may prefer using a desktop application. When you use these apps, all the processing is done on your computer. Nothing is done online. Another advantage is that you don’t have to worry about your image being used in another capacity. This is why it helps to look at Privacy pages or Terms of Service.

Squoosh

Squoosh is a new player on the block from Google Chrome Labs. Like Compressor.IO, it includes many image file formats, including some beta versions. It’s the only service I’ve seen that handles the AVIF format. They also offer sample files you can use for testing.

Like the other services, the process begins by dropping or pasting your file. The initial pass will convert using the same file format. However, you can do additional edits with other file formats. Using a JPEG XL (Beta) option, I got the best compression, which was 4% more efficient than the default pass.

What’s also appealing is the options that show after the first pass. You can also reduce the number of colors via a Reduce palette option and even resize. The only drawbacks I saw were there is no help and I encountered processing errors with the AVIF file type. (Update: 6/13/21 – on a recent update, I was able to convert to AVIF. The converted image size was reduced to 717kb.

The service also looks out for developers and allows you to copy NPX commands or clone the repo from GitHub.

Squoosh test image and result.
Squoosh optimization options

Final Image size: 1495 KB / 15.5% of original.

Microsoft Photos

Another free option that you can use locally is Microsoft Photos. If it wasn’t included with your Windows version, you can download it from the Microsoft Store. Once you upload your photo, you have several ways to reduce the image. You can either resize the image by adjusting the height and width in pixels. Alternatively, you can reduce the image by a percentage. By default, the app will lock your aspect ratio.

You’ll need to double-click on your image to get to the resize option. This will then load it into the editor. You can click the 3 dots menu from there to reveal more options. Midway down is an option for Resize image.

Microsoft Photos more menu options.

This will overlay an additional dialog over your image. You can use the radio button to determine if you want to state your size in pixels or percentages. In addition, the Quality slider drops down to 80%. The example below shows that using the new Quality value reduces the picture size from 9.4 MB to 2.1 MB.

Microsoft Photos Resize Overlay.

Final Image size: 2100 KB / 22.3% of original.

Microsoft Paint

Another Microsoft option is Microsoft Paint. It’s a basic image editor whose functions are even more minimal than Microsoft Photos. The only option for reducing the file size is to reduce the image size. There are no Quality slider or image resolution adjustments. This means if you needed to keep the same image dimensions, this tool wouldn’t work.

Squoosh for the Win

I think all these services did what they claimed, and I would feel comfortable using any of them. If I had to provide a starting point, I would opt for Squoosh. I think it provides the most options, which could be handy if you need to fine-tune your settings. I also prefer having an app.

One item to remember is that these file size reduction results can vary based on the image. I only used 1 image in this test and not a set containing varying colors, sizes, and resolutions. As the saying goes, “Your mileage may differ.”

Newer Image File Formats

While the .JPG image files are ubiquitous, they’re old, and companies are trying to improve them. If you glance at the Squoosh screenshot above, you can see the .AVIF format reduced the picture file size the most. However, too few browsers or software programs support it. You can use services like CanIUse.com to see which browsers support it. The adoption rate is above 80%, but Microsoft Edge doesn’t support it.

Table showing which browsers support AVIF foiles.
CanIUse.com table showing browser AVIF adoption rates

While the AVIF format is still a ways off, the WebP format is a good option for compressing images. I didn’t focus on it because one of the requirements from my reader stated the file needed to be a JPG. The WebP format is used throughout the web because of reduced storage space. In fact, if your browser supports the file format, Cloudflare (our CDN) may serve you this file format. It’s not as efficient as AVIF, but it is well-supported. It’s worth a look the next time you have to reduce the size of your image.

Key Points & Takeaways

The bottom line is if you’re trying to figure out how to reduce image file sizes, there are plenty of options. In addition to my recommendations above, more online tools and compression algorithms are being developed. Google fuels part of this, as they have a need to speed up web crawling. And as we know, each new crop of smartphones has better cameras resulting in larger digital images.

  • Always keep the original images, as some file formats can suffer from pixelation if you try to enlarge them after compression.
  • Two ways to reduce image file size are resizing the image or adjusting the image quality.
  • Image dimensions or pixel density can be reduced using image editing programs like SnagIt, Affinity Photo, Microsoft Paint, or Microsoft Photos.
  • Templated services like Adobe Express can be used to apply predefined templates to uploaded images, effectively resizing them.
  • Photo cropping can also be effective if non-relevant areas can be removed from the image.
  • Desktop applications can also be used for image compression, with the advantage of the processing being done on your computer, not online.
  • And ChatGPT is still a work in progress and mentions there may be an issue with the upload mechanism.