Compress PNG Online Free: Smaller Screenshots & Graphics

PNG without the balloon

PNG stores every pixel exactly as it appears. That's the entire reason these files balloon: nothing gets guessed, quantized or cleverly approximated, so a 4 MB photograph saved as PNG is normal behaviour — and a terrible email attachment.

Three honest moves, in order of impact:

1. Resize first. The single biggest win, before any compression algorithm runs. A 4000×3000 photo is 12 million pixels; an inbox needs maybe 2 of them.
2. For flat graphics, expect the best wins. Icons, logos, illustrations and UI screenshots re-encode losslessly here with all metadata stripped — typically 10–30% off. The 60–90% palette trick is real, but it belongs to a dedicated palette-quantizer; this canvas path is lossless-only and we won't invent numbers for it. If your screenshot is actually a photo, WebP will always beat it.
3. Photographs almost never belong in PNG. Convert them to JPEG or WebP instead and accept lossy — those formats are literally designed for it.

When PNG is unavoidable: logos on colored or transparent backgrounds (JPEG can't do transparency), screenshots of text, and anything where you need the exact pixel-perfect original.

One honest caveat: PNG's lossless promise is about reconstruction, not size. Anything you shrink here keeps every pixel — if the input is already well-optimized, the savings will be modest, and we'll say so rather than pretend.

Palette vs truecolor: what PNG stores

PNG comes in two personalities. Truecolor stores 24-bit pixels (plus optional 8-bit alpha); row filtering — None, Sub, Up, Average, Paeth — and DEFLATE squeeze out redundancy. Palette stores at most 256 indices at 1–8 bits each: an order of magnitude less raw data. A flat UI screenshot at 200 colors shrinks hard once palettized; a photo with a smooth sky shrinks the same way — and bands instead of blending.

Brutal honesty on quantization: it's sampling, not compression. Screenshots tolerate it — their palettes genuinely are small; photos don't: 16.7 million colors shoved through 256 buckets, and the contouring shows.

Two limits, plainly: PNG here is a fresh lossless encode — identical pixels, but EXIF, tEXt and time chunks are gone; the canvas never saw them. The browser can't write palettized PNG at all, so the real levers are pixel count (Max width) and WebP. An already-optimal PNG shrinks modestly — we'd rather say so.

• Truecolor PNG: exact pixels, biggest files; palette PNG: ≤256 colors, tiny, exact
• Quantization suits screenshots; it bands photos — physics, not settings
• Lossless means pixel-exact on decode, never small
• Re-encoding here strips all metadata (EXIF, tEXt, time) — fresh pixels, no baggage
• WebP beats PNG for photos and text screenshots — commonly half the bytes

Keep PNG when tooling demands exact pixels; reach for WebP when only eyes will decode it.