Image Resizer changes the dimensions and file size of your pictures directly on your device using the browser Canvas. Because the work is done locally, your images are never uploaded and stay completely private. Resize by exact pixels or by percentage, and lock the aspect ratio so your photo never looks stretched. It is free, needs no signup, and delivers a resized image in an instant.
How to resize an image
- 1 Select the image you want to resize.
- 2 Enter new dimensions in pixels or percent.
- 3 Keep the ratio locked to avoid distortion.
- 4 Download your resized image.
How the resize is performed
Your file is decoded into an ImageBitmap — a raw pixel buffer the browser can draw quickly — and then painted onto a canvas at the target dimensions. The canvas is created with OffscreenCanvas inside a Web Worker wherever the browser supports it, so a large photo does not freeze the interface while it is being processed; on older browsers the same code falls back to a normal canvas on the main thread. Smoothing is set to high quality, which selects the browser’s better interpolation rather than the fast nearest-neighbour path, so downscaled images stay smooth instead of turning jagged.
The re-encode happens at the same moment. The resized canvas is written straight to a Blob in your chosen format, with the quality slider passed through for the lossy ones. That single-step decode-draw-encode is why the tool is fast: the pixels are never converted to an intermediate format or copied more times than necessary.
One detail matters if your image has transparency. JPEG has no alpha channel at all, so before drawing, the canvas is filled with white. Without that step, every transparent pixel would encode as black — the classic ugly surprise when a logo with a transparent background is saved as a JPEG.
When resizing is the answer
Getting under an upload limit
Job portals and government forms routinely cap uploads at 2 MB while phones produce 5 MB photos. Halving the dimensions cuts the pixel count to a quarter, which usually clears the limit in one pass.
Speeding up a web page
Serving a 4,000-pixel photo into a 800-pixel-wide slot wastes most of the bytes you send. Resizing to roughly twice the display size covers high-density screens with nothing left over.
Email attachments
Most mail servers reject messages over 20–25 MB. Ten holiday photos exceed that easily at full resolution and comfortably fit once resized to 1,600 pixels on the long edge.
Consistent thumbnails
Specifying exact pixel dimensions with the ratio locked gives a set of images that line up in a grid, which is what a product listing or a team page needs.
Why resize images online
Resizing helps you meet upload limits, speed up websites, fit social media formats, or shrink files for email. Locking the aspect ratio keeps your images sharp and correctly proportioned every time. Since all processing runs on your device with Canvas, your photos remain private and the tool is completely free.
What resizing can and cannot do
Resizing is a lossy, one-way operation. Knowing what it destroys saves disappointment:
- Enlarging cannot add detail. Scaling a 500-pixel image up to 2,000 gives you a bigger, softer image — the missing information was never captured and interpolation only guesses.
- The operation is not reversible. Resize down, and the discarded pixels are gone; always keep your original rather than overwriting it.
- Metadata is dropped. EXIF data — camera model, GPS coordinates, capture time — does not survive the canvas round-trip. That is a privacy benefit when sharing photos, and a loss if you were relying on it.
- Saving to JPEG flattens transparency to white. If you need a transparent background, choose PNG or WebP as the output format.
- Extremely large images can exhaust memory. A 100-megapixel panorama needs several hundred megabytes as a raw bitmap before any resizing begins, which some mobile browsers will refuse.
Troubleshooting
- The resized image looks blurry
- Two likely causes. If you enlarged it, blur is unavoidable — the detail does not exist. If you shrank it and it looks soft on screen, you may be viewing it scaled up again; check it at 100%. Aim for roughly twice your final display size so high-density screens have pixels to work with.
- The file is barely smaller than the original
- You probably kept PNG as the output. PNG is lossless and stores photographs inefficiently. For a photograph, switching to JPEG or WebP at 80% quality typically cuts the size by 80% or more with no visible difference.
- My transparent logo now has a white box behind it
- That is the JPEG conversion doing exactly what it must — JPEG cannot store transparency. Re-run the resize with PNG or WebP selected and the transparency is preserved.
Frequently asked questions
Will resizing distort my image?
No. Lock the aspect ratio and both width and height scale together to keep perfect proportions.
Are my images uploaded anywhere?
No. Resizing is handled on-device with Canvas, so your images never leave your browser.
What size should I resize to for the web?
Measure the space the image actually occupies and target roughly double that in pixels, to cover high-density displays. A full-width hero on a typical layout is well served by 1,600–2,000 pixels wide; a thumbnail in a grid rarely needs more than 600. Anything beyond that is bytes your visitors download and never see.
Should I keep the aspect ratio locked?
Almost always. Unlocking it stretches the image, which is immediately obvious on faces and text and is one of the few image errors that reads as unprofessional to everyone. If you need a specific shape, resize proportionally and then crop rather than distorting.
Does resizing remove location data from my photos?
Yes, as a side effect. The canvas process reads pixels and discards every EXIF field, GPS coordinates included. If your goal is specifically to strip metadata before sharing a photo, a resize — even to the same dimensions — accomplishes it.
Are my images uploaded to a server?
No. Decoding, resizing and encoding all happen in your browser, and on most devices the heavy work runs in a Web Worker on your own CPU. You can verify it by watching the Network tab, or simply by going offline and resizing anyway.