Resizing an image *down* discards pixels but shouldn't soften what remains. When the result looks mushy, one of these five things is happening.

1. You Upscaled (the most common cause)

Going from 400 px to 1200 px wide means two-thirds of the pixels never existed — the software interpolates them by averaging neighbours, which is mathematically a blur. No setting fixes this; the detail isn't in the file.

Fix: go back to a larger original. If none exists, accept a smaller display size, or use a genuine AI upscaler (which *invents* plausible detail rather than averaging — better looking, but not a recovery of the truth).

2. The Source Was Already Small or Already Compressed

A photo saved from a chat app or a web page may be 800 px with baked-in compression artifacts. Resizing it — up or down — carries those artifacts along and can make them more obvious.

Fix: source the original file rather than a forwarded/downloaded copy. Send and receive important images as files, not as "photos".

3. Double Compression

Every JPEG save re-quantizes the image. Resize a JPEG, save, resize again, save again, and you're stacking generations of loss. Text and edges show it first.

Fix: do all your edits in one pass — crop, resize, then compress once, from the original. Keep a lossless master (PNG or the camera original) if you'll be re-exporting repeatedly.

4. Wrong Format for the Content

Screenshots, charts and anything containing text are the worst case for JPEG: its compression blurs exactly the sharp, high-contrast edges that letters are made of. Downscaling text also thins strokes below one pixel, where they turn grey.

Fix: use PNG (or lossless WebP) for text and UI images, and avoid shrinking a text-heavy screenshot much at all — crop to the relevant region instead of scaling the whole thing.

5. It Isn't the File — It's the Display

Two frequent illusions:

  • Browser/CSS scaling. A 400 px image stretched to 800 px by CSS looks blurry even though the file is fine. On high-DPI (Retina) screens, an image displayed at its exact pixel size still looks soft — those screens want 2× the pixels of the layout size.
  • Viewer zoom. Zooming past 100% in a photo viewer magnifies pixels; the file is unchanged.

Fix: serve images at 2× the CSS display size for high-DPI screens, and check the actual file at 100% zoom before blaming the resize.

The Rule That Prevents Most of It

Always work from the largest original you have, in one editing pass, in the order crop → resize (down only) → compress once, choosing the format by content type: JPEG/WebP for photos, PNG for text and graphics. Do that and "blurry after resizing" mostly stops happening.