PNG to JPG — Free Online Batch Converter with Transparency Fill, Nothing Uploaded
Converting PNG to JPG is not a matter of changing the extension: every pixel is encoded again. PNG stores each pixel losslessly and can carry an alpha channel; JPG trades a little accuracy for a much smaller file and has no transparency at all, so the question that matters most here is what colour the transparent areas become. This tool fills them with white by default, and you can pick any other backdrop so your export never grows an unexplained black border. The quality slider sets how hard the compression works — the higher the value, the more detail survives and the larger the file; for portraits and landscapes somewhere between 0.8 and 0.9 is usually about right. Portrait shots from a phone are auto-rotated from their EXIF orientation first, and capture time, location, camera model and other metadata are dropped during re-encoding, which makes sharing safer. After a batch import you may change the output format for an individual image, pack everything into a ZIP, or export a CSV list for reconciliation. The .jpg and .jpeg outputs are the same format under two spellings, switchable whenever you like. Compare the result side by side or drag a split line, and use the checkerboard to see exactly what colour replaced the transparency. The whole conversion runs locally in your browser: images are never uploaded and it keeps working offline.
Import images
Target format
The options below switch automatically when you pick a format.
Higher values look better but produce larger files; 0.8 to 0.9 is usually enough for photos.
.jpg and .jpeg are the same format, just two ways of naming the file.
JPG has no alpha channel, so transparent areas are filled with this colour — white by default.
JPG is lossy, so every re-save loses a little more detail; it supports neither transparency nor animation. The browser's built-in encoder only emits baseline JPG, not true progressive JPG.
The target format has no alpha channel, so the fill colour above was applied.
Basic adjustments
0 keeps the original size. Only shrinks, never enlarges — this is not a full resize tool.
Re-encoding in the browser automatically strips EXIF metadata such as capture time, GPS and camera model, which is safer by default. Portrait photos from phones are auto-rotated from their EXIF orientation first.
File naming
Example：photo_converted.jpg
A few honest notes about format conversion
- Conversion always re-encodes the pixels, it is not just renaming the file. Renaming .png to .jpg may still open in some viewers, but uploads, moderation and programmatic parsing often break.
- Lossy output cannot be reversed. Detail and transparency lost in a PNG → JPG conversion will not come back if you convert it to PNG again, so keep your originals.
- Animated images keep only their first frame. Static JPG, PNG and WebP exports all take frame one; use a GIF tool to preserve animation.
- Everything runs locally in your browser. Images are never uploaded, and the tool keeps working offline.
Preview & export
Batch list
After importing several images, their status and size change will appear here.
How to use
- Drag your PNG images onto the page, click Choose images to pick several at once, or press Ctrl+V to paste a screenshot. If you only have a link, paste it into the Image URL field. The tool detects the real format from the file header, so a wrong extension is still recognised.
- Check the quality slider: the default sits just below 90% and suits most landscapes and portraits. If the source is an icon or screenshot with a transparent background, choose a fill colour first — white is the usual choice, but you can match your page's background instead.
- Switch the File extension control if you need .jpeg; .jpg and .jpeg are byte-for-byte the same kind of file. Rotation, flipping, a long-edge limit, and a shared prefix or suffix for a batch are all set in Basic adjustments and File naming below.
- Wait for the converted preview on the right, then compare details side by side or with the split slider and confirm no black border remains before downloading. Multiple images can be packed into a ZIP, or you can export a CSV list that records each source format and new size.
Frequently asked questions
Why did my transparent background turn into a black block?
JPG has no alpha channel at all, so a browser canvas composites transparent pixels against black by default. This tool paints the canvas with the Transparency fill colour before drawing the image — white by default — so black blocks should not appear. If the whole image is still black, you are probably on a very old browser; reselect the fill colour or switch to a current one.
What is the difference between .jpg and .jpeg, and which should I pick?
None. They are the same JPEG format, just a long and a short spelling of the extension. Early DOS systems allowed only three characters after the dot, which is why .jpg stuck; once that limit disappeared, .jpeg became equally valid. Most websites, messaging apps and print workflows handle .jpg most reliably, and only a few legacy programs insist on the full spelling. This page outputs both; switching changes the filename only, not the encoding.
Why is the result larger than the original PNG?
That is common with screenshots, UI captures, line art and flat-colour icons. PNG's lossless compression is extremely efficient on large areas of identical colour, so a few hundred KB for a screenshot is normal. JPG excels at the continuous gradients of a photograph; sharp text edges cost it more bits and pick up noise, and the gap widens as you raise quality. Keep such artwork as PNG, or move to WebP, which supports both lossless encoding and transparency.
Does one conversion lose quality, and can converting back to PNG restore it?
Yes, it loses detail, and it cannot be restored. JPG is lossy: the high-frequency detail discarded during quantisation no longer exists in the file, so converting to PNG merely repackages the already-damaged pixels losslessly. Every further JPG save loses a little more. Keep a PNG or TIFF master while editing and export a JPG only at the final publishing step.
Will phone photos come out sideways, and is my personal data still in the file?
They will not. When a phone shoots in portrait it often stores the pixels landscape and merely writes an orientation flag into EXIF; this tool reads that flag and straightens the image during decoding before conversion starts. Re-encoding produces a brand-new file, so capture time, GPS coordinates, camera model, serial numbers and other EXIF metadata are stripped automatically — safer than sending the original photo.
What is it
The trade-off between the two formats comes down to one sentence: PNG records the exact colour of every pixel, while JPG records an approximation whose difference the human eye is unlikely to notice. JPG first cuts the image into small blocks, applies a discrete cosine transform, rounds away high-frequency detail with a quantisation table, and then uses chroma subsampling to compress colour information more aggressively than brightness. That is why photos with broad gradients shrink dramatically, while one-pixel text edges develop ringing and mosquito noise. PNG works the other way round: prediction plus lossless compression is extremely efficient on large flat areas and hard edges, and every pixel can keep its own opacity. A transparent PNG converted to JPG therefore has to answer one extra question — what colour fills the transparent parts, because unfilled pixels are treated as black.
Origin & history
The story starts with two unrelated threads. In 1986, ISO and what was then the CCITT jointly formed an expert group to define a common compression standard for still photographs — the Joint Photographic Experts Group, or JPEG. Published in 1992, the standard splits an image into eight-by-eight blocks, applies a discrete cosine transform, turns the eye's greater sensitivity to brightness than to colour into compression via a quantisation table, and finishes with Huffman coding. Because the standard defined the bitstream but not how to store it in a file, Eric Hamilton of C-Cube proposed the JFIF interchange format in 1991; the .jpg files we use today are really JPEG streams wrapped in JFIF. The other thread began in late 1994, when Unisys announced licensing fees for the LZW algorithm used by GIF. A group of developers assembled a replacement over a mailing list within days, and the first PNG specification became a W3C Recommendation in 1996 and the international standard ISO/IEC 15948 in 2003. The division of labour was clear from then on: photographs to JPG, interfaces, icons and cut-out artwork to PNG. Yet forms that accept only JPG and old devices that cannot read transparency never went away, which is why this pairing became one of the most searched conversions. Once browsers matured, the job moved onto the local machine: the HTML5 canvas offers toBlob with an image/jpeg type and a quality value between zero and one, backed by the libjpeg-family implementation shipped with the browser. It needs no server and quietly removes the privacy risk of uploading. Interestingly, the standard does define progressive JPEG, but the canvas encoder emits baseline JPEG only; EXIF orientation flags were likewise ignored by web pages for years until createImageBitmap gained orientation-aware decoding. What changed most over these decades was not the compression algorithm but the act of conversion itself — from a command line or a server into something you finish by opening a page, without handing your photos to anyone.
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