What is the difference between JPG and JPEG, and do I need to convert between them?
There is no difference at all. JPG and JPEG are two spellings of the extension for exactly the same format, and the contents of the file are the same. So no conversion is needed, and the format converter treats a .jpeg file as JPEG already and leaves it alone. This is the one case where simply renaming the extension is enough if a platform asks for one of them by name.
Why one format has two names
The format's full name is JPEG, after the group that created it. Older operating systems only allowed three letters for an extension, so it was shortened to jpg. Later systems accepted longer extensions and both names stayed in use: some cameras and programs save .jpg, others .jpeg, and you may also meet .jpe or .jfif on older files or images saved from a browser, all essentially the same format.
What the tool does with each
The Image format converter does not rely on the extension to know the format; it reads the file's first bytes, which are identical for .jpg and .jpeg. So if you add photo.jpeg and choose JPEG, it tells you the file is already JPEG and leaves it unconverted, because re-encoding would change nothing except add loss. Files the tool does convert to JPEG always get the .jpg extension: scan.png, for example, comes out as scan.jpg.
When renaming is enough
Normally we warn against renaming extensions by hand, because calling a PNG file .jpg does not make it a JPEG. Between .jpg and .jpeg it is different: the contents are identical, so the new name fools no program. If a platform or upload form accepts .jpg by name and rejects .jpeg, renaming the file is all you need, with no tool involved.
- Right-click the file and choose Rename.
- Change jpeg at the end of the name to jpg, or the other way round.
- If your system warns that the file may become unusable, confirm: here it will not.
- If you cannot see extensions at all, turn on the option to show file name extensions in your file manager's settings.
Make sure it really is a JPEG
The trick only holds if the file is JPEG inside. Some images saved from the web are named .jpg but are really WebP. To check, add the file to the tool and choose JPEG: if it says the file is already JPEG, renaming is all you need; if it converts it and the row shows WEBP or PNG as its format, download the result, which is a genuine JPEG.
And if your real question is about making the file smaller rather than its name, that is a different job: the Image compressor re-encodes JPEGs at the quality you choose.
Common questions
Is .jpeg better quality than .jpg because the name is longer?
No. Quality is set by the compression settings when the file is saved, not by the extension.
Does upper case, like .JPG, matter?
Not for the format. Some websites treat file names as case sensitive, and the tool always writes the extension in lower case.