Convert PNG to JPG — shrink that giant photo PNG instantly

Why convert PNG to JPG?

PNG was designed for lossless compression: screenshots, diagrams, and logos where every pixel must be preserved exactly. But photographs are the wrong use case for PNG. A 4032×3024 photo taken by a modern phone and saved as PNG will be roughly 10–12MB, because PNG's DEFLATE compression can only squeeze repeating byte sequences — and the complex, noise-filled texture of a real photograph has very few of those. JPG's DCT (Discrete Cosine Transform) encoding, on the other hand, models exactly how human vision perceives luminance and chroma, exploiting the redundancy in smooth gradients and fine texture to achieve 5–8x smaller files with no perceptible quality difference at quality 90. If your PNG is a photo, a screenshot of a photo, or any image captured from a camera, it almost certainly belongs in JPG format.

What you lose and what you gain

Converting PNG to JPG is not free — there are two real trade-offs to know about. First, JPG is a lossy format: it discards a small amount of pixel data on encode. At quality 90, this loss is below the threshold of human perception for photographic content, but it is irreversible. Do not discard your original PNG if you anticipate needing to re-edit the image later. Second — and more important to flag — JPG has no alpha channel. If your PNG uses transparency (a logo on a clear background, a screenshot with a transparent UI layer, a product photo with a cut-out background), the transparent pixels will be composited onto a solid background (white by default) when you convert. For transparent PNGs, consider PNG → WebP instead, which preserves the alpha channel while still achieving meaningful compression. If your PNG is a photo with no transparency, neither trade-off applies in practice: you will gain a 5–8x smaller file with no visible difference.

How to convert PNG to JPG

The entire process runs locally in your browser. No server receives your file. Works offline once the page has loaded once:

1. Click "Convert to JPG →" at the top of this page, or drag your PNG file onto the drop zone on the homepage.
2. ConvertMyPic decodes the PNG using the browser's native PNG decoder — the same decoder that renders every PNG image on the web. This is fast and handles all PNG variants: 8-bit, 16-bit, indexed, grayscale, and RGBA. If your PNG has an alpha channel (transparency), the transparent pixels are composited onto a white background before encode. You will see a preview of the result.
3. The decoded image data is passed to mozJPEG — the Mozilla-maintained JPEG encoder compiled to WebAssembly. mozJPEG applies trellis quantization and smarter quantization tables to produce files 5–10% smaller than libjpeg-turbo at the same visual quality setting.
4. Click the download button. The JPG saves to your Downloads folder. The filename matches the original with the extension swapped — photo.png becomes photo.jpg.
5. Need a different quality level? Open /convert directly to access the quality slider (50–100), an EXIF-strip toggle, and a baseline vs. progressive encoding option. Quality 90 is the recommended default for photos.

File size comparison: PNG vs JPG at different quality levels

Two representative cases: a full-resolution phone photo where JPG always wins, and a 1080p screenshot of UI text where the outcome is more nuanced.

When to convert, and when to stay on PNG

Convert to JPG when your PNG is photographic content: a camera photo saved as PNG, a screenshot of a photo viewer or lightbox, an image you downloaded as PNG from a social platform, or any image that originated from a real-world scene. These images have complex texture that JPG compresses far more efficiently than PNG. Converting them will typically cut file size by 80–90% with no visible quality loss at quality 90. Stay on PNG when your image has hard edges, flat colors, or transparency. Screenshots of text and code look worse as JPG because the DCT ringing artifacts appear as colored halos around the sharp contrast edges of character strokes. Diagrams, charts, logos, and icons that rely on sharp geometric lines suffer the same problem. Any PNG that uses transparency — a UI component, a sticker, a product photo with a clipped background — will lose that transparency when converted to JPG; white fill will replace all transparent areas. A practical rule: if you captured it with a camera, convert to JPG. If you created it in a design tool or captured it as a UI screenshot, keep it as PNG. When in doubt, do a quick test conversion at quality 90 and zoom in on the text and edge regions — JPG artifacts are immediately obvious when they are present.

Under the hood: which codecs are used

PNG decoding is handled by the browser's native image decoder, which every browser ships as part of its standard rendering pipeline. This is the fastest and most compatible path: it handles all PNG sub-formats (including 16-bit depth, interlaced, indexed-color, and grayscale) and requires no additional WASM download. The decoded pixel data is handed off as an ImageBitmap. JPG encoding uses mozJPEG, Mozilla's fork of libjpeg-turbo that has been optimized for output quality rather than encode speed. mozJPEG adds trellis quantization (a brute-force optimization pass that finds better DCT coefficient quantization decisions), improved default quantization tables tuned for perceptual quality, and progressive scan ordering. The net result is files that are 5–10% smaller than standard libjpeg at the same SSIM score. mozJPEG is compiled to WebAssembly and runs in a Web Worker so the main UI thread stays responsive during encode. Source: github.com/mozilla/mozjpeg.