JPG / JPEG (.jpg)
The most widely used format for photographs — small file size with excellent visual quality.
- Extension
- .jpg
- MIME Type
- image/jpeg
Last updated
What Is a JPG File?
JPEG (Joint Photographic Experts Group) was standardised in 1992 as a lossy compression format optimised for photographs. The file extension is typically .jpg or .jpeg — both refer to the same format.
How JPG Compression Works
JPG uses the Discrete Cosine Transform (DCT) algorithm:
- The image is divided into 8×8 pixel blocks
- Each block is transformed from pixel values to frequency coefficients
- High-frequency detail (fine texture) is discarded based on the quality setting
- The result is compressed using Huffman coding
The key implication: each time a JPG is opened and re-saved, the DCT process runs again, introducing additional artefacts. Never use JPG as a working/editing format — only as a final delivery format.
Quality Settings Reference
| Quality | Use Case | File Size vs. Q100 |
|---|---|---|
| 90–95 | Archival, print-ready editorial | −30–40% |
| 80–85 | General web use (recommended) | −60–70% |
| 70–75 | Thumbnails, secondary images | −75–80% |
| Below 70 | Not recommended | −80%+ |
When to Use JPG
✅ Photographs and realistic images ✅ Social media posts (final delivery) ✅ Email attachments where file size matters ✅ Web images alongside WebP fallback
❌ Logos, icons, text-heavy screenshots (use PNG) ❌ Images with transparency (use PNG or WebP) ❌ Working/editing copies (use PNG as intermediate)
MIME Type
image/jpeg — used by web servers, browsers, and APIs to identify JPEG files regardless of whether the extension is .jpg or .jpeg.
Tools for JPG / JPEG files
- Compress Image
Compress JPEG, PNG, and WebP images online without losing visible quality. Reduce file sizes instantly — no upload, runs in your browser.
- JPG to PDF
Convert one or more JPG images to a PDF document online. Combine multiple photos into a single PDF in seconds — free and private.
- JPG to PNG
Convert JPG to PNG online in one click. Lossless output, transparent background support — runs entirely in your browser.
- PDF to JPG
Convert PDF pages to high-quality JPG images online. Each page becomes a separate JPG — free, private, browser-based.
- Resize Image
Resize images online to exact pixel dimensions or a percentage. Works on JPG, PNG, and WebP. No upload — runs entirely in your browser.
- WebP Converter
Convert images to WebP format online, or convert WebP to JPG/PNG. Reduce file sizes by up to 30% — free, private, and browser-based with no upload required.
Related terms
Related terms
- Aspect Ratio
The proportional relationship between an image's width and height, expressed as width:height (e.g. 16:9 or 4:3).
- DPI (Dots Per Inch)
A measure of image resolution — the number of pixels or printed dots per inch. Higher DPI means more detail and larger file sizes.
- EXIF Data
Metadata automatically embedded in JPEG photographs containing camera settings, GPS location, date, and other capture information.
- File Header / Magic Bytes
The first few bytes of a file that identify its format — used by applications to verify file type independent of the file extension.
- Image Resolution
The number of pixels in an image, typically expressed as width × height (e.g., 1920×1080) or total megapixels. Higher resolution means more detail and a larger file size.