How to Convert PNG to JPG (and Why Your Files Are So Big)

You exported a screenshot or a design comp, and the PNG is 4 MB. The email won't send, the CMS rejects it, or you're just watching your storage fill up. Converting it to JPG will typically get you down to a few hundred kilobytes, with no visible quality loss for anything that isn't a logo or a diagram with text.

When You'd Need This

Screenshots. macOS defaults to PNG for all screenshots. So does the Windows Snipping Tool. That's a sensible default (PNG is lossless and renders text crisply) but it means a full-screen screenshot on a retina display can land at 3–6 MB before you've done anything with it. If you're sending screen recordings of bugs, documenting a workflow, or archiving your work, those sizes add up fast.

Design exports. Figma, Sketch, and Adobe XD all export to PNG by default. That's fine for assets with transparency (icons, logos, cutout elements), but if you're exporting a full mockup with a solid background, you're carrying the lossless overhead of PNG for content that doesn't need it. A full-screen Figma frame for a 1440px design might be 5–8 MB as PNG. As JPG at 85% quality, that same frame is often under 500 KB.

Email and CMS limits. Most email clients will refuse attachments over 25 MB (and that's Gmail's limit; others are stricter). CMS platforms like WordPress and Webflow have their own upload ceilings. Even when files technically fit, large images slow down editors and bloat media libraries. JPG is the practical format for sharing finished visuals through any normal channel.

How to Do It

1. Go to quickbrew.tools/tools/png-to-jpg/
2. Drop your PNG file into the upload zone, or click to browse and select it.
3. Adjust the quality slider if you want. 85% is a good default; you won't see a difference from 100% on most images, and the file size drops significantly.
4. Click Convert. Your JPG downloads automatically. Nothing is sent to a server.

What's Actually Happening

PNG stores images losslessly. Every pixel is recorded exactly, and DEFLATE compression (the same algorithm ZIP files use) removes redundant data without discarding anything. That's why PNG files are reliably perfect, and why they're large.

JPG works differently. It converts the image to a different color space (YCbCr, which separates brightness from color), then breaks the image into 8x8 pixel blocks. Each block gets run through a discrete cosine transform (DCT), which expresses the block as a sum of frequency components. The quality setting controls how aggressively the encoder discards high-frequency components.

Transparency doesn't survive this process. PNG supports an alpha channel. JPG has no transparency concept. When you convert a PNG with a transparent background, the converter fills the transparent areas with white before encoding.

Real-world numbers: A 4 MB PNG screenshot typically becomes 300–800 KB as JPG at 85% quality. Photos exported from a camera as PNG see similar or better compression, often 3–5x smaller. Images with large areas of flat color (screencaps of code editors, terminal windows) compress extremely well, sometimes better than 10x.

PNG vs JPG: Format Comparison

	PNG	JPG
Format name	Portable Network Graphics	Joint Photographic Experts Group
Typical file size	Large (lossless storage)	Small to medium (lossy encoding)
Quality model	Lossless, pixel-perfect every time	Lossy, artifacts at low quality settings
Transparency	Full alpha channel support	Not supported
Browser support	Universal	Universal
Best use case	Logos, icons, diagrams, screenshots to re-edit	Photos, finished comps, email, web thumbnails

A Note on Privacy

QuickBrew's PNG to JPG converter runs entirely in your browser via WebAssembly. Your file never touches a server. For screenshots specifically, this matters: screenshots often contain account dashboards, private messages, internal documents, or other content you wouldn't want passing through a third party's infrastructure. With a browser-based converter, the file stays on your machine the entire time.