GIF (Graphics Interchange Format) is an image format limited to a maximum of 256 colors per frame, originally designed by CompuServe in 1987 for efficient image transmission over slow dial-up connections. Converting a JPG photograph to GIF reduces the color palette from 16.7 million colors (24-bit) down to 256 or fewer, using a process called color quantization. This produces a noticeable visual change — smooth gradients in photographs become banded, and subtle color variations are lost.

Despite these limitations, GIF remains useful for specific purposes: it supports animation (multiple frames in one file), it supports binary transparency (fully transparent or fully opaque pixels), and it is universally supported by every web browser, email client, and messaging platform ever created. Converting a JPG to a static GIF frame is the first step toward creating animated GIFs or is used when a platform specifically requires GIF format.

The primary reason to convert JPG to GIF is animation. If you want to create an animated GIF from a series of photographs, each frame must be in GIF format first. Social media platforms, messaging apps, and forums use animated GIFs as a standard for short looping clips, and the format's universal support means your GIF will play everywhere without any codec or plugin requirements.

Another reason is platform requirements. Some older web-based systems, form uploads, and email signature tools only accept GIF format. Certain e-commerce platforms use GIF for product image thumbnails because of its small file size with simple graphics. If your source is a photograph, the quality trade-off is significant, but for product images on white backgrounds or simple graphics that happen to be saved as JPG, GIF conversion can actually produce comparable results with smaller file sizes.

Sharp converts the 24-bit JPG (16.7 million colors) to an 8-bit indexed color GIF using median-cut color quantization. The algorithm selects the 256 most representative colors from the original image and maps every pixel to the nearest palette entry. Dithering (Floyd-Steinberg) is applied to simulate intermediate colors through pixel patterns. The resulting GIF uses LZW (Lempel-Ziv-Welch) lossless compression on the indexed color data.

GIF only supports 256 colors. Your 16.7 million-color JPG photograph is reduced to 256 colors through quantization, and dithering adds a stippled pattern to simulate the missing colors. This is inherent to the GIF format, not a conversion error.

A single JPG converts to a single static GIF frame. To create animation, you need multiple source images (one per frame). Convert each to GIF and combine them using an animation tool.

GIF supports binary transparency — each pixel is either fully transparent or fully opaque. JPG does not have transparency, so converting JPG to GIF produces a fully opaque image. You would need to add transparency in an image editor afterward.

PNG is almost always better for static images. It supports 24-bit color (no 256-color limit), alpha transparency, and better compression for most content. GIF's only advantage is animation support.

GIF files of photographs are often larger than the equivalent JPG, because JPEG compression is far more efficient for photographic content. GIF only produces smaller files for simple graphics with few colors.

Yes, significantly. The JPG-to-GIF conversion loses color information (256 colors only), and converting back to JPG applies additional lossy compression. Each round trip degrades the image further.

Device	JPG	GIF
Windows PC	Native	Native
macOS	Native	Partial
iPhone/iPad	Native	Partial
Android	Native	Native
Linux	Partial	Partial
Web Browser	Native	Native

特徴	JPG	GIF
正式名称	JPEG Image	Graphics Interchange Format
拡張子	.jpg	.gif
最適な用途	Universal support	Animation support

Convert JPG to GIF — Free Online Converter

JPGからGIFへの変換について

JPGをGIFに変換する理由

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