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.gif

GIF test images

Static GIF89a images with a full 256-colour palette and optional transparency, encoded byte for byte in your browser.

Open the .gif generator

Or start from a preset

What is a GIF image?

Short answer

GIF is a palette image format: up to 256 colours, LZW-compressed pixels, and one colour that can be transparent. A file has a header, a logical screen descriptor, a colour table, extension blocks and image data.

Our encoder writes the clear codes and code-size changes every GIF decoder must handle, so large images exercise the full LZW table. Animated GIFs are on the list for later.

Anatomy of a GIF image

  • GIF89aHeader and version
  • Logical screenWidth, height and the global colour table flag
  • Colour table256 RGB entries
  • 21 F9Graphic control extension: transparency
  • 2CImage descriptor, then LZW data in 255-byte blocks
  • 3BTrailer

What you can generate

  • 1×1 to 4000×4000 pixels
  • 6×7×6 colour cube with ordered dithering
  • One transparent palette entry
  • Comment extension
  • Size label in a pixel font

How to make one

  1. Open the GIF image generator, or start from a preset above.
  2. Set the size and switch on the edge cases you need; the preview and size estimate follow every change.
  3. Generate, then download. The file is made in your browser, and the same preset and seed always give you the same file.

Questions

Not yet. Static images are real today; animation is listed for a later release.

A GIF has at most 256 colours, so gradients would show bands. A 4×4 ordered dither spreads the error and keeps the file deterministic.

Related formats