Compress an image to under 500KB

Where the 500KB target comes from

500KB is almost never enforced by a validator. It is a courtesy limit — a number people arrive at because of how other systems behave downstream:

• Email attachments. Your provider may allow 25MB, but the recipient's mail server may not, and corporate filters routinely reject or silently strip larger messages. A handful of 500KB photos gets through essentially everywhere.
• Print-adjacent web use. Images that someone may download and print — a menu, a flyer, an event poster — need real resolution behind them, and 500KB keeps it.
• Portfolio and gallery images. Photography, architecture, interiors, anything a visitor will open full-screen and actually look at rather than glance past.

What 500KB actually looks like

Here is the finding that makes 500KB different from every smaller target on this site. Run through the tool, that same 4K phone photograph (3840 × 2160, 1.52 MB) reached 500KB without its dimensions being reduced at all — 493.2 KB at the full 3840 × 2160, quality 57.

Every tighter target on this site required resizing. 500KB did not. That is the practical dividing line: below it you are choosing between pixels and quality, and at or above it you can usually keep both.

For a photograph destined for print, that matters more than it looks. Keeping the full pixel dimensions means the image still has enough resolution to print at a reasonable size — which a 100KB version resized to 1445px does not.

Emailing photos without annoying people

If email is why you are here, a few things are worth knowing beyond the file size:

1. Total message size is what gets rejected, not any single attachment. Ten 500KB photos is a 5MB email, and some corporate servers still baulk at that.
2. Phone email apps often re-compress for you, sometimes badly and usually without saying so. Compressing deliberately first means you control the result rather than discovering it at the other end.
3. Send as a link for anything over about 10MB total. Cloud storage links do not bounce, do not fill the recipient's mailbox, and let them download only what they want.

If 500KB is more than you need

For anything that lives on a web page rather than in an inbox, it usually is. 200KB is visually equivalent on screen and less than half the weight. Going the other way, if you are tidying up a photo library rather than sending anything, 1MB keeps more headroom for future editing and cropping.