How this works in your browser
The image is decoded onto a canvas, scaled down if you set a width limit, and re-encoded as JPEG at the quality you chose. Both stages reduce size but in fundamentally different ways, which is why the order matters. Resizing removes pixels outright, and since pixel count scales with the square of the dimensions, halving the width discards three quarters of the data while everything that remains stays sharp. Quality reduction keeps every pixel but describes them less precisely, discarding the fine detail human vision is least sensitive to. Photographs absorb that well; text and flat colour do not, which is the one case where the JPEG output is the wrong choice.
Who uses Image Compressor and Resizer
Emailing photos
Bring an oversized camera image under an attachment size limit.
Web page performance
Cut the bytes a page spends on images that display far smaller than their file size suggests.
Upload form limits
Get a photo under a strict size cap on a listing or application form.
Private and client images
Compress confidential photos without uploading them to a service.
Frequently asked questions
What output format does it use?
The compressed output is saved as JPEG, which supports adjustable quality for effective size reduction on photos.
Can I resize without changing quality much?
Yes - set quality near 100% and just reduce the max width to shrink dimensions.
Is my image uploaded anywhere?
No, compression and resizing happen entirely in your browser using the canvas API.
Should I resize or lower the quality?
Resize first, and it is usually not close. Halving an image’s width removes three quarters of its pixels, which cuts far more than a quality adjustment can while leaving what remains sharp. Quality reduction is what you reach for after the dimensions are already right for where the image will be shown.
What quality setting should I use?
Around 80 percent is the common sweet spot for photographs: a large size saving with no difference most people can see. Below about 60 the artifacts start showing in smooth areas like skies and skin. Screenshots and flat graphics degrade sooner, so keep those higher.
Why did my PNG logo come out looking worse?
Because the output is JPEG, which is built for photographs and handles sharp edges and flat colour poorly. A logo or screenshot gains visible fuzz around every line. For that kind of image, resizing while keeping PNG is the better route.
What happens to transparency?
It becomes white, since JPEG has no alpha channel. A cut-out graphic with a transparent background will arrive with a white box behind it, which is worth knowing before compressing one.