Fit, crop or stretch
When the target dimensions have a different shape to your image, something has to give. The three modes handle it differently.
- Fit inside scales the image until it fits entirely within the target, then uses whichever dimension it reached. Nothing is lost, but the result may not be exactly the size you asked for.
- Crop to fill scales until the frame is covered and trims the overflow from the edges, centred. You get exact dimensions at the cost of losing the outer edges — fine for backgrounds, risky for photos where the subject sits near an edge.
- Stretch forces the exact dimensions by distorting the image. It is almost always the wrong choice, and included mainly for the rare case where you are resizing a texture or pattern rather than a picture.
Why upscaling disappoints
Making an image larger cannot invent detail that was never captured. Enlarging a 400px image to 1600px gives you a soft, blurry 1600px image — the browser interpolates between existing pixels rather than adding new information. If you need a larger version, go back to the original file at its full resolution.
Downscaling, by contrast, is nearly always safe and often improves apparent sharpness, because averaging many pixels into one reduces noise.
Common platform dimensions
- Instagram square — 1080 × 1080. Portrait posts use 1080 × 1350, which occupies more screen space in the feed.
- Stories and Reels — 1080 × 1920. Keep important content away from the top and bottom, where interface elements sit.
- YouTube thumbnail — 1280 × 720, under 2 MB.
- LinkedIn post — 1200 × 627 for a link preview.
- Open Graph / social preview — 1200 × 630, the size most platforms crop from when your page is shared.
Platforms re-compress whatever you upload, so there is little point supplying an image far larger than the display size. Matching the target dimensions gives you control over the crop instead of leaving it to their algorithm.
Sizing for your own website
Measure the width the image actually occupies on the page and resize to roughly twice that for high-density screens. An image displayed in an 800px column wants to be around 1600px wide, not 4000px. This single change usually does more for page speed than any compression setting.
Frequently asked questions
Are my images uploaded?
No. Resizing happens in your browser using the Canvas API. Nothing is sent, and there is no file size limit beyond your device's memory.
Does resizing reduce file size?
Yes, substantially — dimensions affect file size more than any quality setting. Halving both width and height removes about three quarters of the pixel data.
Will transparency be preserved?
Only if you keep PNG or WebP output. Converting to JPG replaces transparent areas with white, since JPG has no alpha channel.
Does it remove EXIF data?
Yes. Re-encoding through the canvas strips metadata including camera model and GPS coordinates — useful before publishing photos.