PNG → JPG

Convert PNGs to JPG with quality control. Free, no upload. 1 GB max · Up to 1 GB · Processed locally, never sent to a server.

A PNG exported from an image editor, or a full-screen screenshot, often runs to several megabytes, when the same picture as a JPG would fit in a few hundred kilobytes. Some administrative forms and print services accept nothing but JPG in any case. This tool does one thing: it takes PNG files, the picker accepts nothing else, and produces a JPG for each one.

The conversion happens in three stages. The PNG is decoded at its original resolution, the background colour you chose is painted underneath the image to fill the transparent areas, then the JPEG encoder built into your browser writes the final file at the quality level set on the slider. Only two settings are exposed, because they are the only two that change anything: quality, from 40 to 100 %, and the colour that replaces transparency.

Every file produced comes with its size before and after. If the JPG turns out heavier than the original PNG, the note says so and points out that PNG remains better suited to logos and flat colour; the file is delivered all the same, and you are the one who decides. Nothing is uploaded, the conversion runs in the open tab.

How to use it

  1. Drop your PNG files The drop zone filters on the image/png type and the .png extension. You can drop several in a row, then remove any of them from the list before you start.
  2. Set the JPG quality The slider runs from 40 to 100 % in steps of 5 and starts at 90 %. Lower down, the file is light but sharp edges get dirty.
  3. Choose the background colour White, Black or Light grey. That colour is painted permanently under the transparent pixels of the PNG, since JPG has no way of representing them.
  4. Click Run The progress bar names the file being handled. Images are converted one after another, at their original dimensions, with no resizing.
  5. Compare the sizes before downloading Under each result you get the original size, the size obtained and, where relevant, the warning that the JPG is the heavier of the two. The ↓ Download all (ZIP) button groups the batch.

What happens to the alpha channel

A PNG stores four values per pixel: red, green, blue and alpha, the last one describing the degree of opacity. A JPG stores only three. Transparency is therefore not "lost" in the sense of a damaged file: there is simply nowhere for it to be written in the destination format.

Before encoding, the tool paints a rectangle of the chosen colour behind the whole image. Fully transparent pixels take that colour as it stands. Semi-transparent pixels, typically the anti-aliased edge of a logo, blend with it according to their opacity: an outline at 40 % opacity over white becomes a permanently pale pixel.

The operation cannot be undone. Converting the JPG back to PNG will give you an alpha channel again, but a fully opaque one: the white that filled the background has become part of the image. If the visual may one day have to sit on another colour, keep the original PNG beside it.

Which quality and which colour to choose

The default setting, 90 %, suits the great majority of photographs: the degradation stays hard to see on a screen, while the weight drops sharply. Below 70 %, artefacts appear wherever two solid colours meet, in the form of a dull fringe around lettering.

The background colour is chosen according to where the image will end up: white for a document or an attachment, black for a visual headed to a dark interface, the light grey #f2f2f2 for the content blocks of many themes, where it avoids the white rectangle that stands out around a logo. Since the colour is baked into the file, a bad choice can only be corrected by starting again from the PNG.

When it is better not to convert

JPG was designed for photography, that is, for images whose colours vary continuously. Faced with a logo, an icon, a chart or text, its compression works against the grain: it produces files that are sometimes bigger than the PNG, and soiled edges. Hence the warning shown when the result exceeds the size of the source file.

Two alternatives are worth examining before converting. To make a PNG lighter and nothing more, the Compress an image tool optimises it without touching a displayed pixel, transparency included. For something light that keeps transparency, that same tool produces WebP, which does handle the alpha channel.

What the output file does not carry over

The image passes through a canvas before being re-encoded: the file obtained holds the pixels and nothing else, neither the text chunks of the PNG nor the embedded colour profile. Encoding relies on the JPEG codec of the browser, not on MozJPEG, which only comes into play in the compression tool. Files are accepted up to 1 GB, with a warning past 400 MB depending on the memory available.

Frequently asked questions

Can I get the transparency back from the JPG?

No. The alpha channel no longer exists in the converted file, and the colour that replaced it is part of the image. You have to start again from the PNG, or cut the subject out once more.

Why is my JPG heavier than the PNG I started from?

Because your image is made of flat colour and sharp edges. PNG encodes those very efficiently, JPG encodes them badly and spends bytes trying to reproduce them. The note under the file flags this case.

Which quality for a screenshot containing text?

None will really satisfy: even at 100 %, small text loses its crispness. For a screenshot, keep the PNG and make it lighter with the compression tool instead.

Can I drop a JPG, a WebP or a HEIC here?

No, the picker is limited to PNG. For the other formats, WebP to PNG, HEIC to JPG and Compress an image cover the common cases.

Are the images converted at the same resolution?

Yes, the width and the height in pixels stay those of the original file. To change the dimensions, go through Resize an image.

How many PNG files can I process at once?

As many as the memory of the device allows: they are handled one after another, and the ZIP button gathers the JPG files obtained into a single archive.

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