PNG to JPG

Turn PNG files into smaller JPG images, and decide what colour sits where the transparency was.

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What this tool does

PNG to JPG decodes your file, paints it onto a canvas and hands that canvas to the JPEG encoder your browser already ships, at the quality you chose. PNG records every pixel exactly, while JPG discards detail the eye is poor at noticing, and that discarded detail is where the saving comes from. A photograph that was stored as PNG usually comes out several times smaller with nothing visibly different about it.

JPG has no alpha channel, so something has to happen to transparent pixels before they can be written at all. The tool paints the background colour you choose — white unless you change it — and composites the image on top, which is what it means to flatten transparency. Fully transparent areas become that colour, and semi-transparent ones, including the soft edges of a logo, are blended with it, so a logo flattened onto white keeps a pale fringe when it later sits on a dark page.

Nothing leaves the tab. The page reads the file straight from disk, encodes it in memory and gives the JPG back for saving, with no copy kept anywhere else. Several PNGs can be queued together and each is converted on its own under the same settings, giving one JPG per input file named after the original, with a ZIP offered once there is more than one. The ceiling is your own machine: a very large PNG still has to fit in memory as a canvas, and past the browser's limit the encode is reported as a failure rather than quietly handing back something else.

One thing this tool deliberately does not do is second-guess you: whatever the quality setting produces is what you get, even when the JPG turns out larger than the PNG it came from. That happens with screenshots, diagrams, text and flat areas of colour, where PNG is genuinely the better format and JPG adds visible ringing around sharp edges as well as bytes. The result screen totals the bytes going in and coming out and lists each finished JPG at its own size, so a file that grew shows up rather than slipping past — and when one does, keep the PNG.

How to use it

  1. Add your PNG files. The picker is filtered to .png, and there is no cap on how many go in at once. Each file is converted on its own under the same settings, so five in gives five out, each named after the PNG it came from with .jpg on the end.
  2. Set the quality. The slider covers 10 to 100 per cent and begins at 88, which most photographs survive with no visible change. Below about 60, gradients start to band and hard edges pick up a halo.
  3. Choose what goes behind the transparency. The colour control starts on white. Set it to the colour of the page, slide or listing the picture will sit on, and the flattened edges will match their surroundings instead of announcing themselves.
  4. Decide whether the picture also needs shrinking. Maximum width stays at 0 unless you change it, and at 0 the pixel dimensions are untouched. Any other figure caps the width and the height follows the aspect ratio; nothing is ever enlarged, and a steep reduction is stepped down in halves, which is what stops a shrunken photograph looking ragged.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

A photograph that was saved as PNG

Design exports and screen captures routinely produce PNG photos many times larger than they need to be, with nothing gained, because the format keeps every pixel intact whether that helps or not.

An upload form that only accepts JPG

Job applications, visa and exam portals and older content systems often reject .png outright, whatever the picture inside it happens to be.

Putting a transparent logo onto a fixed background

Marketplace listings frequently demand a plain white backdrop. Flattening it here means the shop's own viewer is not left to decide what goes behind the alpha channel.

Trimming a set of images before emailing them

Converting a folder of PNGs at one quality setting is usually enough to bring a batch under an attachment limit, without cropping anything or leaving files behind.

Questions

Is my PNG uploaded anywhere?
No. The decode, the background fill and the JPEG encode all take place on your own machine, in this tab, through the canvas the browser provides — so the picture never travels, and the page carries on working with no network at all.
What happens to the transparent parts of the image?
They are filled with the background colour before encoding, because JPG cannot record transparency at all. Semi-transparent pixels are blended with that colour rather than preserved, so choose the colour the image will actually sit on.
Why is my JPG larger than the PNG was?
Because JPG is built for photographs. Screenshots, line art, text and broad flat colour compress badly under it and well under PNG. The file you asked for is still written, and the before and after totals on the result screen show what happened, so you can look and then keep the original.
How much control is there over the encoder?
Quality, and nothing beyond it. Chroma subsampling, progressive scans and the quantisation tables are decided by the browser's own JPEG encoder, and those choices differ from one browser to the next, so the same PNG at 88 will not encode to identical bytes, or necessarily to the same size, everywhere.
Can I get the PNG back afterwards?
Not the one you started with. JPG to PNG will produce a PNG again, but the detail the JPEG encoder threw away is gone for good and the new file is usually larger than the JPG. Keep the PNG if you may need to edit it later.
Does the JPG keep anything from the PNG besides the pixels?
No. Re-encoding through the canvas writes a fresh image, so text chunks, embedded colour profiles and any other ancillary data in the PNG are not carried across, and a 16-bit-per-channel PNG comes through at the canvas's 8 bits.
What about animated PNG files?
Only one frame survives. The canvas draws a single still image and JPG has no way to store a sequence, so an APNG comes out as one picture rather than an animation.

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