JPEG or JPG: nothing changes in the picture
JPEG stands for Joint Photographic Experts Group, the committee that published the standard in 1992. The format is called JPEG, and its media type is image/jpeg, with no "jpg" anywhere in it. The shorter .jpg ending is a leftover from the DOS and early Windows era, when a file extension could have only three letters. Windows no longer has that limit, and other systems never did.
So a file ending in .jpeg and one ending in .jpg are the same format, and renaming one to the other changes nothing inside. MDN's list of extensions for JPEG also includes .jpe, .jfif and .pjpeg. This page accepts the common ones.
What really changes when JPEG becomes PNG
- The pixels stay the same. PNG compresses without loss, so it stores exactly what the decoded JPEG contains. The blocky patches and softness from JPEG compression are still there, now stored exactly.
- The file gets much bigger. JPEG gets small by discarding detail. PNG keeps all of it. Our 945 KB photo became 4.5 MB, nearly five times larger. The lower the JPEG quality, the smaller the PNG, because less detail is left to store: the same photo saved at quality 30 (204 KB) gave a 2.6 MB PNG, and saved at quality 95 (1.2 MB) it gave 4.5 MB.
- Nothing is added. There is no transparency to restore and no lost detail to recover. A PNG made from a JPEG is fully opaque.
- Later edits are safer. A PNG can be edited and saved again without further loss, which JPEG cannot. This is the real reason to convert before you start editing.
If your goal is a smaller file, the other direction is the one to use: PNG to JPEG.
A name is not a format
Many sites serve a picture whose address ends in .jpeg or .jpg but whose content is another format, such as WebP or AVIF. A file saved from such a page keeps the wrong ending. This tool does not trust the ending. It reads the first bytes of the file, so a WebP renamed to .jpeg was recognised in our test, shown as WebP in the list, and converted normally.
That also means you can drop mixed folders on this page. Files that are not pictures are reported with a plain message, and the rest carry on. The other converter pages, such as JPG to PNG, use the same engine.
Colour, rotation and metadata
A JPEG that your camera stored sideways with an orientation tag is turned the right way up in the PNG, and it matched Pillow's upright version of the same file exactly. Colours are converted to sRGB and no colour profile is written, so a wide-gamut photo may look slightly less vivid. A Display P3 JPEG came out within 1 level of a LittleCMS conversion to sRGB; without that step its colours would have been off by 3.2 levels on average and by up to 38.
We also converted JPEG files saved in other ways and compared them with Pillow's decoder. Baseline, progressive, full resolution colour, quality 30 and quality 95 files all came out pixel for pixel identical, and so did a CMYK JPEG. A grey JPEG became an 8 bit grey PNG of 1.7 MB, against 4.5 MB for the colour version of the same photo.
EXIF data, such as the camera, the date and the GPS location, is removed by default, which is the safer choice before you share a picture. With Keep, the EXIF block is copied from the JPEG into the PNG. In our test the PNG received the make, model, date, artist and the GPS position, with the orientation tag set to 1 because the picture itself was already turned. The colour profile and XMP are never copied.