什么是 JPG (JPEG)?
JPG (JPEG) 是一种有损图像压缩格式，开发于 1992 年，由于其出色的质量与小文件大小的平衡，广泛用于照片和网页图像。
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What is it?
JPG（也写作 JPEG - 联合图像专家组）是一种于 1992 年创建的有损图像压缩格式。它是互联网上、数码相机和智能手机上使用最广泛的图像格式。
该格式通过丢弃人眼最不容易注意到的图像数据来工作，从而实现显著的文件大小减少。高质量的 JPEG 文件可以比同一图像的未压缩版本小 10 倍，几乎没有可见的质量损失。
Technical Specifications
Pros & Cons
Advantages
Dramatic compression with minimal visible quality loss - up to 10x smaller than uncompressed.
Supported by every browser, device, camera, and operating system in existence.
Quality setting 1–100 gives full control over the size vs quality trade-off.
Perfect for photographs and complex images with millions of colors and gradients.
Disadvantages
Each save re-compresses the image causing gradual quality degradation over time.
Does not support alpha channel - transparent areas are filled with white.
Blocky artifacts appear at low quality settings especially around sharp edges.
Not suitable for text, logos, or flat-color graphics - use PNG or SVG instead.
When to Use It
JPG 是大多数摄影内容和文件大小优先的场合的正确选择。
Photography
Digital cameras and smartphones save photos as JPG by default. Perfect for portraits, landscapes, and natural scenes.
Web Images
Smaller file sizes mean faster page loads. Use JPG for all photographic web content.
Social Media
Most social platforms re-compress uploads to JPG. Upload as JPG for predictable quality control.
Email & Sharing
Small JPG files are easy to share via email and messaging apps without hitting size limits.
需要转换或压缩 JPG 吗?
使用我们的免费在线工具压缩 JPG 文件，将 JPG 转换为 PNG、WebP、PDF 等 - 无需注册。
免费试用 JPG 工具Frequently Asked Questions
What is the difference between JPG and JPEG?
There is no difference - they are the same format. JPG became common because early Windows limited extensions to 3 characters.
Does saving a JPG multiple times reduce quality?
Yes. Each save re-applies lossy compression causing gradual degradation. Keep originals in PNG and export to JPG only as a final step.
What quality setting should I use for JPG?
For web use quality 70–80 is ideal. For print use 85–95. Quality above 95 rarely makes a visible difference but significantly increases file size.
Can JPG files have a transparent background?
No. JPG does not support transparency. Use PNG, WebP, or SVG instead. JPG fills transparent areas with white by default.
Is JPG or PNG better for web images?
For photographs JPG is smaller. For graphics and text PNG is better. For modern web use, WebP outperforms both.