Resizing changes an image’s dimensions in pixels, for example from 4000 px wide to 1200 px. Compressing keeps the dimensions but stores the pixels more efficiently, which reduces the file size in KB or MB. For the smallest sharp images, resize to the size you actually display first, then compress.
What is the difference between resizing and compressing?
| Resize | Compress | |
|---|---|---|
| What changes | Width and height in pixels | How the pixels are stored |
| Example | 4000 × 3000 → 1200 × 900 px | Same pixels, smaller file |
| Effect on file size | Big drop when making images smaller | Moderate to big drop |
| Effect on quality | None visible if the new size is still larger than the display size | Little visible change at sensible settings |
| Best for | Websites, social media, forms with pixel rules | Saving bandwidth and storage, email, KB limits |
Both make files smaller. They are strongest together.
Why does image size matter for websites?
Images are often the heaviest part of a web page. Big image files take longer to download, especially on mobile data. That slows down how fast the main content appears, which affects the visitor’s experience and page speed scores such as Largest Contentful Paint.
A common mistake is uploading a full phone photo, several thousand pixels wide, and showing it in a space only 800 pixels wide. The browser downloads every pixel, then throws most of them away.
When should I resize an image?
Resize whenever your image has more pixels than it needs. Good rules of thumb:
- Blog or article images: about the width of your content area. If you want sharp images on high-density phone screens, use up to twice that width.
- Full-width hero images: around 1600 to 2000 px wide is usually plenty.
- Thumbnails: match the display size, or double it for sharp screens.
- Forms: the exact pixel size the form asks for.
How to resize an image
- Open the Resize Image tool and add your images. Batch resizing is supported.
- Choose Resize by: Size (px, cm, mm or in) or Percent.
- Type the new width. With Keep aspect ratio ticked, the height updates automatically.
- If you turn off the aspect ratio, pick what happens when the shape differs: Stretch, Crop to fill or Fit with background.
- Choose the output format and quality, then click Resize images.
When should I compress an image?
Compress every image you put online, after resizing. Compression removes data your eyes are unlikely to notice.
How to compress an image
- Open the Compress Image tool and add JPG, PNG or WebP files.
- Set Quality. Lower means a smaller file. Around 70–85% looks the same to most people.
- Optionally change the Output format, for example to WebP.
- Optionally set a Max width to resize and compress in one step.
- Keep Never make a file bigger than the original ticked. If a file is already well optimized, the tool keeps the original.
- Click Compress images and download the files or a ZIP.
For PNG files, the tool reduces the number of colours to save space. This works very well for screenshots and graphics. For photos, JPG or WebP is usually much smaller than any PNG.
What is the best order: resize first or compress first?
Resize first, then compress. Compressing a huge image and then resizing it means the image is saved twice, which can add extra quality loss. Resizing first also gives the compressor fewer pixels to store, so you can keep a higher quality setting for the same file size.
The Compress Image tool’s Max width option does both in the right order in a single step.
Which format gives the smallest files?
For websites, switching from JPG to WebP is often an easy win, because WebP is usually smaller at similar quality. The JPG to WebP converter handles many files at once. Keep JPG for places where WebP is not accepted, like many upload forms.
What if I need an exact file size?
Online forms often ask for a limit such as “under 100KB”. Instead of guessing a quality number, use the Compress to KB tool. It finds the best quality that fits, and only reduces dimensions if needed.
Example: from a phone photo to a fast web image
Imagine a phone photo that is 4000 × 3000 pixels and several megabytes. Your blog shows it 800 pixels wide.
- Resize to 1600 px wide (twice the display width for sharp phone screens).
- Compress at about 80% quality and choose WebP.
- Check it at 100% zoom. The file is now a small fraction of the original size, and it looks the same on the page.
A simple image checklist for faster pages
- Resize to the largest size the image is actually displayed at (or twice that for sharp screens).
- Compress at around 75–85% quality.
- Use WebP for websites where possible, JPG for photos elsewhere, PNG for screenshots and logos.
- Keep your original files in a separate folder in case you need to edit again.
- Check the result at 100% zoom before publishing.
Following these steps for every new image keeps your pages light without any special software. All the Img Stop tools above run in your browser, so you can prepare images on any computer or phone, and your files stay on your device.
Key takeaways
- Resize changes pixels; compress changes how pixels are stored.
- Resize first, then compress, for the best quality at the smallest size.
- Quality around 70–85% usually looks the same as the original.
- WebP is a strong choice for website images.
- Use a target-size tool when a form gives you a strict KB limit.
Frequently asked questions
Does resizing an image reduce its quality?
Making an image smaller removes pixels, but if the new size is still at least as large as where it is shown, it looks just as sharp. Making a small image bigger is different: it cannot add real detail and often looks soft or blurry.
Does compressing an image reduce its resolution?
No. Normal compression keeps the same width and height in pixels. It only changes how the pixel data is stored. Only a target-size tool may lower the dimensions, and only when quality alone cannot reach the size you asked for.
What quality setting should I use when compressing JPG?
Between 70% and 85% is a good starting point for photos. Most people cannot see a difference from the original at those levels, while the file becomes much smaller. Go lower only if you need a very small file, and check the result.
What is the best image size for a website?
Use the width the image is actually displayed at, or up to twice that width for sharp images on high-density screens. Full-width images rarely need more than about 2000 pixels. Then compress and consider WebP for smaller files.