JPG to PNG Converter

What the JPG to PNG Converter Does

A JPEG is already compressed and lossy. Converting it to PNG gives you a lossless container for those exact pixels — useful when you are about to edit the image repeatedly, need a format an app demands, or want to add transparency the JPEG could never hold.

What it will not do is improve the picture. PNG faithfully stores whatever the JPEG decoded to, artefacts and all; it cannot reconstruct detail the original compression discarded. Expect the same image, in a bigger, lossless file.

How It Works

The browser decodes your JPEG and draws it onto an HTML5 canvas at full size. JPEG has no transparency, so the canvas simply holds the opaque photo.

The canvas is exported as a PNG. PNG encoding is lossless — the quality value browsers accept is ignored for PNG — so every pixel currently on the canvas is stored exactly. You download a .png with the same dimensions and base name.

Processing pipeline

1. Step 1. Drop in a JPG (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, and the photo is drawn onto it.
3. Step 3. The canvas is encoded as a PNG — lossless, so the quality setting is ignored.
4. Step 4. Every pixel is stored exactly as decoded; nothing further is discarded.
5. Step 5. The .png downloads with your original filename; dimensions are unchanged.

Privacy

Conversion runs entirely on your device. The JPG is decoded and re-encoded in the page's memory and the PNG is produced locally — no upload, no server copy.

Nothing is stored and there is no account. Refresh or close the tab and both images leave memory — safe for private photos and documents.

Technical Details

Standards & references

• ISO/IEC 10918 (JPEG) — the lossy source format. Its compression is already baked in before conversion, and PNG cannot reverse it.
• ISO/IEC 15948 (PNG) — the lossless target — DEFLATE compression plus an optional alpha channel, storing the decoded pixels exactly.
• HTML Canvas API — toBlob('image/png') encodes losslessly; for PNG the browser ignores any quality argument.

Accuracy & Limitations

This conversion is lossless going forward but not restorative. PNG records exactly what the JPEG decoded to — including any blocking or halo artefacts the JPEG already had — and cannot rebuild detail that was discarded when the JPEG was first saved.

Expect the file to grow, often substantially. PNG's lossless compression is far less efficient on photographic content than JPEG's lossy compression, so a photo saved as PNG is typically several times larger than the JPG.

The output is opaque. A JPEG has no transparency to carry over, so the PNG is fully opaque — though it is now in a format where you can add an alpha channel in an editor later.

Dimensions are preserved exactly; the tool never resizes. Very large images just use more memory during encoding.

Real-World Use Cases

When to use it — and when not to

If you want a smaller file, keep the JPG or convert to WebP; PNG is the choice when you need lossless or transparency, not a size cut.

Frequently Asked Questions

References

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

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