JPEG Image (MIME: image/jpeg) is the most widely used image format on the web, known for its efficient lossy compression that dramatically reduces file sizes while maintaining acceptable visual quality for photographs and complex images.
History and Development
JPEG was created in 1992 by the Joint Photographic Experts Group (ISO/IEC 10918-1). It quickly became the standard format for digital photography and web images. The format has remained largely unchanged since its introduction, though JPEG 2000 (2000) and JPEG XL (2021) have been introduced as successors. Despite newer alternatives, JPEG remains dominant due to universal browser and device support, accounting for over 70% of images on the web as of 2024.
Technical Specifications
- Compression: Lossy (DCT-based), adjustable quality 1-100
- Color depth: 24-bit (8 bits per channel, 16.7 million colors)
- Color spaces: sRGB, Adobe RGB, CMYK (for print)
- Max resolution: 65,535 × 65,535 pixels
- Transparency: Not supported
- Animation: Not supported
- Metadata: EXIF (camera data), IPTC (caption/copyright), XMP
- Progressive loading: Supported (baseline vs progressive JPEG)
Common Use Cases
JPEG is ideal for photographs, social media images, product shots in e-commerce, email attachments, and any scenario where file size matters more than pixel-perfect quality. Digital cameras save in JPEG by default. Web developers use JPEG for hero images and photo galleries. It's the standard format for sharing images via messaging apps and social platforms.
JPG vs Similar Formats
- JPEG vs PNG: JPEG is smaller but lossy; PNG is lossless with transparency support. Use JPEG for photos, PNG for graphics with text or transparency.
- JPEG vs WebP: WebP offers 25-34% smaller files at the same quality, plus transparency. However, JPEG has universal legacy support.
- JPEG vs AVIF: AVIF achieves 50% smaller files than JPEG at similar quality, but browser support is still growing.
How to Open and Edit
JPEG files open natively in every major operating system (Windows, macOS, Linux, iOS, Android) and all web browsers. For editing, use Adobe Photoshop, GIMP (free), or online tools like Canva. Mobile users can edit JPEG in built-in Photos apps. For bulk processing, tools like ImageMagick (CLI) or XnConvert are recommended.
Frequently Asked Questions
What is the difference between JPG and JPEG?
There is no difference — JPG and JPEG are the same format. The ".jpg" extension exists because older Windows systems only allowed 3-character extensions. Modern systems accept both.
Does JPEG support transparency?
No. JPEG does not support transparency (alpha channel). If you need transparent backgrounds, use PNG, WebP, or AVIF instead.
How much quality loss occurs with JPEG compression?
It depends on the quality setting. At 80-90% quality, compression artifacts are barely visible. Below 50%, blocking artifacts become noticeable. Each re-save at lossy quality degrades the image further (generation loss).
What is the maximum file size for a JPEG?
The JPEG standard supports images up to 65,535 × 65,535 pixels. File size has no formal limit but depends on resolution and quality. A 12MP photo at 90% quality is typically 3-5 MB.