How to compress images without visibly losing quality

Lever 1: resolution

A modern phone photo is around 4000 × 3000 pixels. Most screens display images at under 2000 pixels wide, and a form preview might show it at 400. Halving the width and height cuts the pixel count — and roughly the file size — by 75% with no visible change at normal viewing sizes.

Lever 2: quality setting

Lossy formats discard detail the eye is least sensitive to. The relationship between quality and size is not linear: going from 100 to 85 often halves the file, while going from 85 to 70 saves much less and starts to show blocky artefacts in skies and skin tones.

A setting between 75 and 85 is the sweet spot for photographs. For screenshots with text, prefer PNG or WEBP lossless, since JPG blurs sharp edges.

Lever 3: format

Choosing a newer format can deliver the biggest single win:

• JPG — universal, good for photos, no transparency.
• PNG — lossless, ideal for logos, screenshots and transparency; large for photos.
• WEBP — typically 25–35% smaller than JPG at equal quality, supported by all modern browsers.
• AVIF — often 50% smaller than JPG, but slower to encode and less widely accepted by forms.

A reliable workflow

First resize to the largest dimension you actually need. Then export at quality 80 and check the result at 100% zoom. If the file is still too big, lower quality in steps of 5 rather than jumping straight to 50. Only switch format if the destination accepts it — many official portals still require JPG.