File size explained
File size depends on the number of pixels, the format, and the compression settings. PNG keeps every pixel but usually creates larger files. JPG and WebP remove redundant data to shrink the file. AVIF can shrink even more, especially for photos.
Comparison table: size vs dimensions
| Term |
What it means |
How to fix issues |
| Pixel dimensions |
Width and height in pixels |
Resize to the display size |
| File size |
Storage weight in KB or MB |
Compress or change format |
| DPI |
Print density |
Important for print, not web |
| Aspect ratio |
Shape of the image |
Keep it locked to avoid distortion |
Real-world use case: blog images
A blog layout uses 1200x630 for feature images. If you upload 4000x3000 photos, the page becomes heavy. Resize to 1200x630 and compress to around 150 KB. The image looks the same to readers but loads much faster.
Common misunderstandings
DPI does not change a web image. It only affects print output. Another misconception is that smaller file size always means lower quality. If you use a better format and modern compression, you can get smaller files with nearly identical visual quality.
How to read image properties quickly
Most operating systems show image dimensions and file size in the file inspector. On the web, you can also use your browser dev tools to see the rendered size versus the intrinsic size. The intrinsic size is the actual pixel dimensions of the file. The rendered size is how large it appears on the page. When the rendered size is larger than the intrinsic size, the image will look blurry. When it is smaller, you are sending more pixels than needed.
Practical rules of thumb
- Match pixel dimensions to the largest display size.
- Use compression to reduce file size without reducing dimensions.
- Avoid changing aspect ratios unless you want a stretched look.
- Keep a high quality master file for future exports.
These simple rules prevent most issues and make your image workflow more predictable.
Optimize in stages instead of all at once
Many problems happen when you try to solve everything in a single step. A better approach is to optimize in stages: resize first, then adjust clarity if needed, then compress for delivery. This gives you more control and reduces the chance of artifacts.
Naming and storage habits that save time
Use descriptive names like "product-hero-1200w.webp" so you can identify assets quickly. Store files in a simple structure and keep versions organized. Good naming makes it easier to reuse assets and avoid mistakes, especially when working on multiple projects.
Common pitfalls to avoid
Avoid converting between lossy formats multiple times. Do not upscale small images beyond their limits. Do not ignore the display size. These pitfalls are easy to avoid with a short checklist and a consistent workflow.
Detailed workflow example
A practical way to apply this topic is to work from a simple example. Start with a high quality original, decide the final destination, and then make one clean export. If the image is for a website, determine the largest display size, resize to that size, and pick the right format. If the image is for social, use the platform dimensions and keep enough margin for cropping. This approach is consistent and avoids the trial-and-error loop that often leads to quality loss.
Troubleshooting and quality review
If the result looks worse than expected, step back and review the order of operations. Check for accidental upscaling, verify the aspect ratio, and compare the original and final at the same zoom level. If artifacts appear, reduce compression or switch formats. If the image looks soft, confirm the target size and apply only light sharpening. Most issues are caused by one of these three steps, so fixing them usually brings the image back to a clean result.
Delivery checklist
- Confirm the output dimensions match the display size.
- Verify format and quality settings are correct for the content.
- Preview on at least one real device.
- Save a master file for future edits.
- Keep filenames descriptive and versioned.
This checklist is short, but it keeps your workflow reliable and makes results easy to reproduce.
Summary
Pixel dimensions control how large an image appears. File size controls how fast it loads. To fix blurry images, resize to the correct dimensions. To fix slow pages, compress or convert.
