JPG — also written JPEG, which stands for Joint Photographic Experts Group — is the most widely used digital image format in existence. Chances are the last photo you took on your phone was saved as a JPG. Understanding why JPG works the way it does will help you know when to use it and, just as importantly, when to use something else.
How JPG Compression Works
JPG uses lossy compression. This means the format actively discards some image data to make the file smaller. It does this cleverly — targeting subtle color variations the human eye struggles to perceive, especially in complex scenes like a beach or a forest. The result is a file that looks nearly identical to the original but can be 10–20x smaller.
The trade-off: every time you save a JPG, the compression runs again and discards a little more data. Edit and save a JPG ten times and you'll start to see compression artifacts — blocky smears around sharp edges and text. This is why professionals keep master copies in lossless formats (RAW or TIFF) and only export as JPG for final distribution.
When to Use JPG
JPG excels with real-world photography — images with millions of colors, smooth gradients, and complex textures:
- Digital photography — Cameras and smartphones default to JPG for good reason: great quality at manageable file sizes.
- Website images — Product photos, blog headers, and background images load faster as JPGs.
- Social media posts — Most platforms recompress uploaded images anyway, so a good-quality JPG is the right starting point.
- Email attachments — Sending a photo? JPG keeps the file small enough to actually deliver.
When NOT to Use JPG
JPG struggles with sharp edges, solid flat colors, and text. Save a screenshot of a spreadsheet as a JPG and you'll notice ugly fuzzy artifacts around every letter. The same applies to logos, diagrams, charts, and icons. For those, PNG preserves every pixel perfectly — at the cost of a larger file size.
JPG also doesn't support transparency. If you need an image with a transparent background (like a logo to layer over a webpage), use PNG instead.
JPG vs. PNG vs. WebP
JPG is best for photographs. PNG is best for graphics, screenshots, and anything requiring transparency. WebP is a newer Google format offering better compression than both — but isn't universally supported in older software. For most everyday tasks, JPG and PNG remain the practical defaults.
Frequently Asked Questions
Does a JPG lose quality every time you open it?
No — simply opening and viewing a JPG does not degrade it. Quality is only lost when you save or re-export the file, triggering the compression algorithm again. If you open a JPG, view it, and close it without saving, it's unchanged.
What JPG quality setting should I use?
Most photo editors let you choose a quality level from 1–100 when saving as JPG. For web images, 75–85 is the sweet spot — excellent visual quality with significant file size reduction. For professional print work where images will be enlarged, use 90–95.
What's the difference between .jpg and .jpeg?
Nothing. They're identical formats. The .jpg extension became standard on early Windows systems, which required three-letter extensions. Mac and Unix systems used .jpeg. Today both extensions work everywhere and produce identical files.
JPG Tools
- JPG to PDF — Turn a collection of photos or scanned receipts into a single, organized PDF document.
- PDF to JPG — Extract individual pages from a PDF as high-quality JPG images.