PNG to JPG Converter

What the PNG to JPG Converter Does

PNGs are lossless and often large — great for screenshots and graphics, heavy for photographs. Converting to JPG trades PNG's perfect fidelity for a much smaller file, which is what you want when the image is a photo and size matters more than pixel-perfect edges.

There is a catch worth knowing up front: JPEG has no transparency. Anything see-through in the PNG is painted onto a solid white background during conversion, because white is the colour this tool fills the canvas with before drawing your image.

How It Works

Your PNG is decoded by the browser and drawn onto an HTML5 canvas at its original width and height. Before the image is drawn, the canvas is filled with white, so transparent pixels end up white rather than black or undefined.

The canvas is then exported as a JPEG at quality 0.92 (92%). JPEG compression runs in the browser — nothing is uploaded — and you download a .jpg with the same dimensions and the same base filename as the original.

Processing pipeline

1. Step 1. Drop in a PNG (any common image works). It is decoded locally — never uploaded.
2. Step 2. A canvas is created at the image's exact width and height.
3. Step 3. The canvas is filled white, then your image is drawn on top — flattening any transparency.
4. Step 4. The canvas is encoded as a JPEG at 92% quality.
5. Step 5. The .jpg downloads with your original filename; dimensions are unchanged.

Privacy

The conversion happens entirely on your device. The PNG is read straight from disk, drawn and re-encoded in the page's memory, and the JPG is produced locally — no copy is uploaded to NineClip or anyone else.

There is no account and nothing is stored. Close the tab and both images are gone from memory, which makes it safe for screenshots, documents, and anything you would rather not hand to a server.

Technical Details

Standards & references

• ISO/IEC 15948 (PNG) — the lossless source format — DEFLATE-compressed, with an optional alpha (transparency) channel that JPEG cannot keep.
• ISO/IEC 10918 (JPEG) — the lossy target format. It uses 8x8 discrete-cosine-transform blocks and has no transparency, so the alpha channel is discarded.
• HTML Canvas API — toBlob('image/jpeg', 0.92) performs the in-browser JPEG encoding; the quality value used is 0.92.

Accuracy & Limitations

JPEG is lossy: at 92% quality the loss is hard to see on photographs, but sharp edges, fine text, and flat areas of solid colour can pick up faint blocky or halo artefacts the original PNG did not have. For line art, logos, or screenshots, PNG (or WebP) usually looks cleaner.

Transparency does not survive. Any see-through region becomes solid white, because the canvas is filled white before your image is drawn. If you need to keep transparency, JPEG is the wrong target — stay on PNG or use WebP.

Dimensions are preserved exactly — the tool does not resize — so the size saving comes purely from JPEG compression, not from fewer pixels.

Everything runs in your browser's memory. Very large images use more memory during the draw-and-encode step, but typical photos convert almost instantly.

Real-World Use Cases

When to use it — and when not to

Keep transparency or crisp edges with PNG; for a smaller file that still supports transparency, try PNG to WebP.

Frequently Asked Questions

References

• HTMLCanvasElement: toBlob() — MDN
• Image file type and format guide — MDN
• ISO/IEC 15948:2004 — Portable Network Graphics (ISO)
• The JPEG standard, ISO/IEC 10918 (ANSI)

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