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Image Compressor
Image Compressor online, free and private. Process images instantly on your device.
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Thumbnail Creator
Make a thumbnail that fits within a maximum size while keeping the aspect ratio — and it never enlarges a small image. Downloads as a PNG.
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Quick Answer
Set a maximum size in pixels and the tool shrinks your image so its longer side fits within that box, keeping the aspect ratio. It only ever scales down — a small image is left at its original size, never blown up. The default max is 300 pixels and the result downloads as a lossless PNG, all in your browser.
What the Thumbnail Creator Does
This makes a thumbnail — a smaller version of your image that fits within a maximum size you set. The aspect ratio is kept, so nothing is stretched, and the longer side ends up at or below your chosen limit.
Crucially, it only shrinks. If your image is already smaller than the maximum, it is left untouched rather than enlarged, because upscaling would only add blur.
How It Works
Drop or pick an image and set the maximum size in pixels.
The tool works out a single scale factor — the smaller of the max divided by the width and the max divided by the height — capped at 1 so it never enlarges. The image is redrawn at that scale.
Download the thumbnail as a PNG. Nothing is uploaded.
Processing pipeline
- Decode locally. Your image is drawn onto a canvas in the browser — never uploaded.
- Work out the scale. Take the smaller of max divided by width and max divided by height, capped at 1 so it only shrinks.
- Redraw smaller. The image is drawn at that scale, keeping the aspect ratio.
- Export the PNG. The thumbnail is saved as a lossless PNG with your original base name.
Fit-within-a-box scale
scale = min( maxSize ÷ width , maxSize ÷ height , 1 )
output = (width × scale) by (height × scale)Worked example
A 1200 × 800 image with max 300: scale = min(0.25, 0.375, 1) = 0.25, so the thumbnail is 300 × 200.The min with 1 is what stops it ever enlarging — a small image keeps its original size.
Privacy
Your image is resized entirely in your browser and never uploaded — there is no server.
No account and no stored copy; the thumbnail exists only on your device.
The canvas re-encode means the thumbnail carries no EXIF or GPS metadata from the original.
Technical Details
| Fit | Longer side at or below the max |
|---|---|
| Default max | 300 pixels |
| Aspect ratio | Preserved |
| Scaling | Down only, never enlarges |
| Output format | PNG (lossless) |
| Metadata | EXIF/GPS stripped |
| Processing | 100% in-browser |
Standards & references
- Fit-within-a-box — The image is scaled so its longer side fits the maximum, keeping the aspect ratio, rather than forced to exact dimensions.
- Downscale only — The scale is capped at 1, so an image already smaller than the maximum is left unchanged rather than enlarged.
Accuracy & Limitations
It fits the image within a square box of the maximum size, so the longer side ends up at or below the maximum and the shorter side is smaller still. It is not an exact width-by-height resize.
It never upscales. An image already smaller than the maximum comes out unchanged, because enlarging it would only soften the result without adding detail.
The aspect ratio is preserved, so the thumbnail is never stretched or squashed.
The output is a lossless PNG. For the smallest possible file at thumbnail size, run it through a converter or compressor afterwards.
Real-World Use Cases
List and gallery thumbnails
Shrink images to a consistent maximum size for a grid or list.
Faster page loads
Make small preview images so a page is not loading full-size photos.
Email and chat previews
Produce a lightweight version to share quickly.
Consistent sizing
Cap a set of mixed-size images to the same maximum.
When to use it — and when not to
Good for
- Fitting images within a maximum size
- Keeping the aspect ratio automatically
- Making lightweight preview images
Not the best choice for
- Exact width-by-height output — use the resizer
- Enlarging a small image — it only shrinks
- Cropping to a shape — use the cropper
For exact pixel dimensions use the image resizer; to crop to a specific shape use the image cropper.
Frequently Asked Questions
What does the max size control?
It is the limit for the longer side. The image is scaled so its longer side fits within that many pixels, and the shorter side scales to match, keeping the aspect ratio.
Will it enlarge a small image?
No. The scale is capped at 1, so an image already smaller than the maximum is left at its original size. Enlarging would only add blur, not detail.
Does it keep the aspect ratio?
Yes, always. It uses a single scale factor for both dimensions, so the thumbnail is never stretched or squashed.
How is this different from the resizer?
The resizer sets exact width and height. This fits the image within a maximum box, picking the scale for you and never upscaling — handy when you just want everything under a certain size.
What format do I get?
A PNG, which is lossless. If you need a smaller file, run the thumbnail through a converter or compressor.
What is the default size?
300 pixels for the longer side, which suits most list and gallery thumbnails. You can set any maximum you like.
Does it crop the image?
No. It scales the whole image down to fit; nothing is cut off. To crop to a shape, use the cropper.
Does it keep transparency?
Yes. The output is PNG, so a transparent image stays transparent at thumbnail size.
Is my image uploaded?
No. The resizing happens entirely in your browser, with no server and nothing stored.
Why is my thumbnail not exactly the max size?
Only the longer side reaches the maximum. The shorter side is proportionally smaller, because the aspect ratio is preserved.
Does it strip metadata?
Yes. The canvas re-encode removes EXIF and GPS data, so the thumbnail carries no camera or location tags.
Can I make several thumbnails at once?
This handles one image at a time. Repeat it with the same maximum to keep a set consistent.
References
Scales the image down to fit inside your chosen maximum box, keeping the aspect ratio, and never upscales (the scale is capped at 1) — a lossless PNG made entirely in your browser.
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Ready to try the Thumbnail Creator?
It is free, private and runs entirely in your browser — no sign-up, no uploads, no limits.