How to Use Image Resizer

Key Takeaways

When constrain proportions is on, changing width automatically updates height (and vice versa) to preserve the original aspect ratio

No — upscaling (making an image bigger than its original size) adds pixels by interpolation, which creates blur or pixelation

For standard displays: match the CSS display size

Resizing to smaller dimensions reduces file size significantly

What is Image Resizer?

Image Resizer scales an image to any width and height you specify — with optional aspect ratio lock to prevent distortion. Resize product photos, blog images, social assets, and UI mockups to exact dimensions without a design app.

Serving an oversized image and letting CSS shrink it wastes bandwidth. A 4000px wide photo displayed at 800px is 25× more pixels than needed. Resize first, then serve.

Resize Modes

Constrain Proportions

Lock the aspect ratio — changing one dimension auto-adjusts the other. Prevents stretching.

Free Dimensions

Set width and height independently. Use when you need a specific canvas size (e.g. for a template).

Percentage Scale

Resize to X% of the original. 50% = half the dimensions = roughly quarter the file size.

Max Dimension

Set a maximum width or height — the image scales down if it exceeds the limit, never up.

Upload your image

Drag-and-drop or click to upload. Original dimensions and file size are shown immediately.

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Enter target size

Type the desired width and/or height in pixels. Toggle the lock icon to constrain proportions.

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Preview the result

See the new dimensions and estimated file size before downloading.

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Download

Save the resized image. Output format matches the input (PNG stays PNG, JPEG stays JPEG).

Recommended Image Sizes

Use Case	Width	Height	Notes
Blog hero	1200 px	630 px	OG image spec
Product thumbnail	400 px	400 px	Square for grids
Profile picture	400 px	400 px	Then crop to circle
Retina display	2× CSS size	2× CSS size	Divide by 2 in CSS
Email header	600 px	auto	Max email width

Tips & Common Mistakes

Resize before compressing, not after. Get dimensions right first, then run through Image Compressor. Compressing a large image first and resizing after wastes effort.

Never upscale images. Enlarging a small image beyond its original resolution creates blur. If you need a larger image, source a higher-resolution original.

Use max-width CSS instead of serving multiple sizes manually. For responsive layouts, serve one image at 2× the max display width and let CSS scale it down. Use srcset for more advanced optimization.

Image Compressor — reduce file size after resizing
Image Cropper — crop to the right area before resizing
JPG to PNG Converter — change format if needed after resize

Frequently Asked Questions

What does 'constrain proportions' mean?

When constrain proportions is on, changing width automatically updates height (and vice versa) to preserve the original aspect ratio. This prevents distortion — the image scales uniformly.

Will resizing to a larger size improve quality?

No — upscaling (making an image bigger than its original size) adds pixels by interpolation, which creates blur or pixelation. Always start with a high-resolution source.

What resolution should I use for web images?

For standard displays: match the CSS display size. For retina/HiDPI screens: use 2× the CSS display size (e.g. a 400px wide container gets a 800px image). Don't go larger than necessary.

Does resizing affect file size?

Resizing to smaller dimensions reduces file size significantly. A 2000px image resized to 800px is roughly 84% smaller in pixel count, which translates to much smaller file size after compression.

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