Overview
JPEG takes its name from the Joint Photographic Experts Group, the committee that published the standard in 1992. JPG and JPEG are the same format: the three-letter .jpg extension comes from older Windows versions that only allowed three-character extensions.
A JPEG stores a photo using compression tuned to human vision. It discards fine colour detail and high-frequency information the eye barely notices, so a 24-megapixel photo that would take about 70 MB as raw pixels usually fits in a few megabytes.
Practically every browser, operating system, camera, phone and image editor can open JPEG files, which makes it the safest choice when you do not know what the recipient will use.
Advantages
- +Universal support on every device, browser and app
- +Excellent compression for photographs
- +Adjustable quality to balance size and fidelity
- +Carries EXIF metadata and ICC colour profiles
- +Progressive mode shows a preview while loading
Disadvantages
- −No transparency
- −Lossy: every re-save loses a little more detail (generation loss)
- −Visible artefacts around sharp edges, text and flat graphics
- −No animation
- −Baseline JPEG is limited to 8 bits per channel
How JPG compression works
JPEG converts the image from RGB into YCbCr (one brightness and two colour channels) and usually stores the colour channels at reduced resolution (chroma subsampling). The image is split into 8×8 pixel blocks, each transformed with a discrete cosine transform (DCT). The resulting frequency coefficients are divided by a quantisation table — this is where the quality setting acts and where information is discarded — and the result is packed losslessly with Huffman coding. Encoders such as MozJPEG squeeze out a further 5–15% with smarter quantisation and coding without lowering visual quality.
Common use cases
- Photos on websites and social media
- Email attachments and messaging
- Camera and smartphone photos
- Printing photos at high quality settings
Browser and software support
Supported by every web browser, operating system, image editor and camera since the 1990s.
How to convert JPG
Use the converter at the top of this page: drop your file, choose an output format and download the result. Conversions run in your browser, so nothing is uploaded.
Processed locally in your browser
JPG FAQ
Is JPG the same as JPEG?
Yes. .jpg, .jpeg and .jpe are different extensions for exactly the same format. You can rename one to the other without converting.
What JPEG quality should I use?
For websites, 75–85 is usually indistinguishable from the original at a fraction of the size. For printing or archiving, use 90–95. Quality 100 produces much larger files for very little visible gain.
Does JPEG support transparency?
No. Transparent areas must be filled with a colour when saving as JPEG. Use PNG, WEBP or AVIF if you need transparency.
Why do JPEGs get worse every time I save them?
Each save decodes and re-compresses the image, discarding a little more detail. Edit in a lossless format and export to JPEG once at the end.