Convert PNG to JPG
Most people arrive here with a screenshot: a PNG the capture tool wrote losslessly at retina resolution, four megabytes of it, and an upload box that stops at two. JPG is the fix, and on anything photographic it is a very good one — a tenth of the original size is an ordinary result. What it costs, and where it costs the most, is worth two minutes before you download.
Nothing is uploaded. Every image stays in this browser tab —here is how that works.
Why the screenshot is four megabytes
A screenshot on a modern display is captured at twice the size it appeared on screen — a 1,440-pixel-wide window lands on disk as a 2,880-pixel-wide image. Nothing in it is thrown away, so a page of colourful interface, a chart, or anything with a photograph inside it runs into the megabytes without doing anything unusual.
That tells you where the size actually is. Most of it is resolution nobody will ever look at, and the rest is the encoder faithfully recording gradients and anti-aliased edges. Setting a max width of around 1,600 pixels before you convert usually takes more off the file than anything else you could do to it.
Let the encoder hit your number
If there is a hard limit at the other end — a 2 MB attachment cap, a 500 kB CMS field, a forum that stops at one megabyte — type it into max file size in kB rather than guessing at the slider. The encoder probes at the quality you asked for, then at its floor, and searches between the two for the highest quality that still fits under your figure.
That is a better answer than trial and error, because it converges on the best-looking file that clears the limit rather than the first one you happen to try. It is also the setting to use when you are doing thirty images at once and cannot inspect each result.
JPEG is worst at exactly what a screenshot is made of
This is the one thing to check before you download. JPEG was built for photographs — smooth, noisy, continuous tone — and a screenshot is the opposite: black text on white, hairline borders, flat panels of colour, hard edges everywhere. Around those edges JPEG leaves a faint grey shimmer, and coloured text on a coloured background can smear outright, because the format stores colour at half the resolution of brightness.
On a screenshot that is mostly photograph or mostly chart, none of this is visible. On a screenshot of a code editor, a spreadsheet or a terminal, small type can end up looking grubby in a way that no setting entirely fixes. Zoom into the text in the preview, not the picture.
When to shrink the PNG instead
If the image is interface, a diagram, a logo or anything with large flat areas, try halving its dimensions and keeping it as a PNG first. Flat colour is precisely what PNG compresses well, and a 1,400-pixel-wide PNG of an app window is frequently both smaller than the full-size JPG and completely crisp.
And if the destination is a web page rather than somebody’s inbox, WebP will beat both of them at any size you care to pick. JPG is worth reaching for when you know nothing about what will open the file — not when you already know it is a browser.
What changes when you convert PNG to JPG
Transparent areas become white — Trade-off
The target format has no alpha channel at all, so transparency has to be resolved into a real colour before encoding. Anything see-through — a rounded logo corner, a cut-out product shot, a drop shadow fading to nothing — is composited onto white. If the image will sit on a dark background, that halo will be obvious, and PNG or WebP is the conversion you actually want.
This is the first lossy step for these pixels — Trade-off
The encoder discards detail it judges you will not miss, and the quality slider decides how much. That trade is what buys the size reduction, and it is irreversible — converting back later restores the format, never the detail. Start at the default and lower it only until you can see the difference, then go one step back.
JPEG opens absolutely everywhere — Benefit
This is the one format with no compatibility question attached: every browser, every phone, every photo frame, every twenty-year-old print kiosk. If something rejected your file and you are not sure why, JPEG is the answer that ends the conversation.
Your PNG is pixel-exact, so this is the first loss it has seen — Note
PNG stores every pixel exactly as it was written, which means the file you are starting from is the best version that has ever existed. Anything lossy you convert it to is a one-way step — keep the PNG if it is a master copy and treat the output as a distribution format.
Camera and location metadata are not carried over — Note
EXIF is dropped: the camera model, the exposure settings, the timestamp, and — the one that matters — the GPS coordinates of where the photo was taken. That is a privacy improvement for anything you are about to publish and a loss if you were relying on it for cataloguing. Orientation is the exception: it is applied to the pixels, so the image stays the right way up.
Output is sRGB — Note
Everything this tool writes is in sRGB, the colour space the web assumes. That is what makes the result look the same in a browser, a chat app and a photo viewer without an embedded profile to carry around.
Questions people ask about this conversion
Will the JPG look worse than the PNG?
On a photograph, not in any way you will notice at the default quality of 80. On a screenshot full of small text and one-pixel borders, possibly — so look at the preview at full size first. That is where JPEG artefacts are easiest to see and hardest to get rid of.
Does converting change the image dimensions?
Not unless you ask. The output is the same pixel size as the input until you set a max width or height. The one exception is a file-size target the encoder cannot reach on quality alone, where dropping dimensions is its last resort rather than its first move.
Can I convert a whole folder at once?
Yes. Drop them in together — several are processed in parallel across your CPU cores, and there is no file-count limit because there is no server to impose one. Download all hands the finished set back as a single ZIP.
Is JPG the same thing as JPEG?
The same format with two spellings. The three-letter extension is a leftover from MS-DOS, which allowed only three characters; .jpg and .jpeg files are identical inside, and anything that opens one opens the other. Use whichever the form in front of you asks for.
Related
Other things you can turn a PNG into
Try it with your own file
Drop an image in and see the result before you download anything.