You can hardly imagine today's digital world with countless blogs and websites filled with images without image optimization. Reducing the size of images you upload on your site or share on social media or email ensures smooth website performance, better user experience, and even improved SEO. But when it comes to optimizing your images, you’ll often face different options: reducing pixel size, compressing file size, or changing the file’s format.

This article will explore two of these approaches. While 4K Image Compressor, our tool for image optimization, specializes in reducing file size, we’ll also dive into how you can reduce pixel dimensions using other tools. When you understand both options, you are better equipped to choose the best method for your needs.

What Is Pixel Size Reduction?

Pixel size reduction refers to changing an image's dimensions, namely its width and height. When you reduce the pixel dimensions of an image, you are essentially shrinking it. This can result in a smaller file size as well, though not always. But more importantly, reducing pixel size often impacts the clarity and detail of an image.

You might want to reduce the pixel dimensions of an image for a number of reasons, including:

Web optimization: Smaller images load faster, which is essential for improving page load times.
Mobile optimization: When displaying images on mobile devices, you may want them to fit into smaller screens.
E-commerce sites: Smaller images load quicker, improving the shopping experience for users.

How to Reduce Pixel Size of an Image Using Resizing Tools

To reduce pixel size, you'll need specialized tools that allow you to resize an image’s width and height directly. Here are a few common methods:

Adobe Photoshop

Photoshop’s “Image Size” function lets you easily adjust pixel dimensions. Simply open your image, choose ‘Image Size,’ and enter the desired dimensions (in pixels).

To reduce the file size of a PNG in Photoshop, follow these steps:

Open the PNG file in Adobe Photoshop by dragging and dropping the image into the application or using File -> Open.
Navigate to Image -> Image Size or press Ctrl+Alt+I.
In the Image Size Dialog box, decrease the Height/Width of the image to compress its size. Ensure that the option to constrain proportions is selected.
Click on the Resample button and choose Bicubic Sharper from the list to maintain image sharpness during compression.
Click OK to close the Image Size dialog box and save the compressed image.

If you’re looking for an analog for Mac, you can use Pixelmator Pro. It works similarly to Photoshop but is a bit easier to use.

GIMP (Free Software)

GIMP offers similar functionality to Photoshop. You can resize images by going to ‘Image’ and selecting ‘Scale Image.’ Here, you can input the exact width and height.

Online Tools

Websites like Pixlr, ResizeImage.net, and Simple Image Resizer offer quick solutions. Upload your image, enter the desired dimensions, and download the resized file.

Here’s how to do it on Pixlr right in your browser.

Open Pixlr in your browser.
Upload the image you want to resize.
Click on "Resize" and adjust the dimensions (width and height) as needed.
Save the resized image to your device.

Reduce Pixel Size of an Image with Preview (Mac)

macOS comes with Preview, which is a user-friendlier analog of Photoshop and a versatile tool for simple image edits:

Right-click the image file and select Open with Preview.
In Preview, head over to the Tools menu and select Adjust Size.

Enter the desired width and height. Make sure you switch the size type (e.g., inches to pixels) if necessary.

Ensure the aspect ratio is locked to prevent distortion.
Tap OK to confirm and then save the resized image by selecting File > Save.

What Is File Size Compression?

File size compression works differently. Instead of changing the image’s pixel dimensions, it focuses on reducing the overall size of the file itself measured in KB, MB, or bytes. The beauty of this approach is that it doesn’t alter the image's width and height. Instead, it reduces the file size by compressing image data, which can help improve loading times without sacrificing visual quality.

Compression is perfect for images you want to keep at a high resolution, such as:

Blog photos or high-quality graphics
Product images for e-commerce sites
Social media posts, where quality is important but file size should be small for quick loading

Reduce an Image Size in KB or MB with 4K Image Compressor (Windows, Mac, Ubuntu)

4K Image Compressor is a desktop application that can easily and quickly optimize JPEG, PNG, HEIC, and WEBP images as well as PDF files. Besides, all file formats (except PDF) can be converted to other formats, supported by the app. In addition to compressing single images one by one, the tool can also optimize images in bulk saving both storage space and your time.

Open 4K Image Compressor.
Select the output format and compression value.

In the Optimization tab, choose File Size and set the number of kilobytes or megabytes you want to reduce the image size to. Here, you can also choose bytes and percentage of the compression.

Click the Compress button, select your image, and click Open.
Hover over the compressed image preview and click the folder icon to locate the file.

Unlike resizing tools, 4K Image Compressor reduces file size without changing the image’s pixel dimensions. It achieves this by compressing the image data, allowing the image to retain its quality but take up less space on your device or website.

Key Differences Between Pixel Size Reduction & File Size Compression

Though both methods are here to make images smaller, they do so in different ways.

Image Pixel Size Reduction

It directly reduces the width and height of an image, giving smaller images as a result, but with a potential loss of clarity and detail. This reduction involves changing the number of pixels in an image which can be done by either increasing (upsampling) or decreasing (downsampling) the pixel count. Resizing changes the dimensions of the image, affecting both its visual size and the amount of data required to represent it. Downsampling reduces the number of pixels, which makes the image smaller, while upsampling adds pixels, potentially making it appear sharper.

Reducing pixel size decreases the file size because fewer pixels mean less data to store.

Best used for: Thumbnails, profile pictures, or any image that doesn’t need to retain high resolution.

File Size Compression

It reduces the overall file size (in KB, MB, bytes) without changing the pixel dimensions and maintains the original resolution and clarity, but the image takes up less storage space. This is achieved by encoding the image data more efficiently, often using algorithms that exploit the redundancy in the image data. It reduces the file size by removing or grouping data, making it easier to store and transmit without altering the number of pixels. So it reduces file size significantly, which is beneficial for web use, as it speeds up page loading times.

Best used for: Web and social media images, where fast loading times and high-quality visuals are both important.

Both methods have their place, and in some cases, you may even want to use them together. For instance, you could resize an image to a smaller pixel dimension and then compress it further with 4K Image Compressor for optimal results.

Choose the approach that best suits your needs and experiment with different tools to achieve the perfect balance between size and quality.