JPEG 转 JPG 转换器

The JPEG standard dates from 1992, when MS-DOS and early Windows only allowed three-character file extensions under the 8.3 naming rule. ".jpeg" did not fit, so ".jpg" became the default on PCs, while Mac and Unix systems kept the full spelling. Digital cameras followed the PC habit: the DCF standard that almost every camera uses names files like DSC_0042.JPG.

The result today is a mix. Photos straight off a camera end in .JPG, files from some Mac apps and web downloads end in .jpeg, and a folder that collects both looks untidy and sorts badly. Some batch scripts, photo-library imports and upload validators also match only one spelling, for example a filter written as *.jpg that quietly skips every .jpeg sitting next to it.

Because both extensions describe the same JPEG data, this page does not decode or re-encode anything. It reads your file, checks that the first three bytes are the JPEG start marker (FF D8 FF), and saves the identical bytes under a .jpg name. A 4.2 MB photo comes out as a 4.2 MB photo, byte for byte the same, and the size readout shows no change.

That matters more than it sounds. Converters that push every file through a canvas re-compress the JPEG, which costs a little detail each time and drops the EXIF block. Here the camera model, capture date, ICC colour profile, orientation flag and any GPS coordinates all stay inside the file. If you want location data removed before sharing, a plain rename will not do it; you need a tool that re-encodes the image or deletes its metadata.

The typical job is a folder where camera shots end in .JPG and downloaded or exported pictures end in .jpeg. Drop the .jpeg files here (up to 30 per drop, 50 MB each, and you can keep adding more) and each one gets the lowercase .jpg ending while the part before the dot stays as it was: holiday-03.jpeg becomes holiday-03.jpg. Download them one at a time, or use Download all to get a single ZIP; if two files end up with the same name, the ZIP keeps both by saving the second as name-2.jpg.

If a file turns out not to be JPEG inside (a PNG or WebP that someone renamed to .jpeg, which happens with images saved from websites), copying it would only hide the problem. In that case the tool decodes it and writes a real JPEG at 92% quality instead, so every file you download is what its name says.

The copy happens in your browser tab. The file is read from your disk into memory, given its new name and handed back as a download; no server sees it, and closing the tab clears it. Since there is no re-encoding, even a batch of large camera files finishes almost at once, limited only by how fast your device reads them.