JPG 转 JPEG 转换器

Most software treats .jpg and .jpeg as equals, but not all of it. Upload validators that compare the extension against a fixed list, a CMS or asset pipeline configured for *.jpeg, a coursework or grant portal whose instructions say "JPEG files only", and build scripts on case-sensitive Linux servers are the usual places where a perfectly good .jpg is refused or ignored. Browsers send the same image/jpeg MIME type for both spellings, so the extension is the only thing those checks are looking at.

The opposite habit exists too: a team or photo library may standardise on .jpeg so that every file in a shared folder follows one pattern. Either way, the fix is a rename, not a format change.

Each file is checked for the JPEG start-of-image marker (the bytes FF D8 FF) and then saved unchanged under the .jpeg extension. Nothing is decoded, so there is no generation loss, the file size stays exactly the same (a 1.8 MB scan stays 1.8 MB), and embedded data such as EXIF, the colour profile and the orientation flag remain where they were. The name before the dot is kept: DSC_0042.JPG becomes DSC_0042.jpeg.

This is also why there is no quality slider on this page. A tool that offers one for JPG to JPEG is re-compressing your photo for no reason, and every pass through a JPEG encoder throws a little more detail away.

Images saved from the web sometimes carry a .jpg name while holding PNG or WebP data, because the site served a different format than the address suggested. A form that inspects the content would reject such a file even after a rename. When the first bytes are not a JPEG marker, this tool decodes the image and encodes a genuine JPEG at 92% quality, filling any transparent areas with white, so the .jpeg you download really is one.

Add up to 30 files per drop (50 MB each) and keep dropping more if you need to; each is renamed on its own and offered as a download, or bundled into one ZIP with Download all. Everything runs in the browser tab you have open: files are read from your device, renamed in memory and handed back, with no server involved and nothing stored after you close the page. A folder of 200 photos becomes a few drops and one ZIP, rather than 200 manual renames in a file manager.