GIF Analyzer

What this tool does

Shows the internal structure of a GIF file and diagnoses why it is large. Use it to see where the problem is before shrinking a GIF.

Steps

1. Upload a GIF file.
2. Check the screen size, frame count, play time and repeat info in "Summary".
3. Read the problems that affect size or playback in "Diagnostics".
4. Check each frame's size, delay and data size in the "Global palette" and "Frames" tables.
5. If needed, "Copy summary" copies text and "Save JSON" saves the whole structure.

Settings

• Summary: version, screen size, file size, frame count, play time, average frames per second, repeat, number of global colors, average frame size, number of frames using transparency, number of frames with a local color table and comments.
• Diagnosis items: frames with a delay under 0.02 seconds (browsers may play them with a 0.1-second delay, which can make playback appear slower), size concentrated in big frames (the top 10% of frames, at least 1, hold 60% or more of all data, when there are 5 or more frames), over 100 frames, 2 or more frames with a local color table, a multi-frame GIF with no repeat info, and a screen over 1,000,000 pixels.
• Frame table: number, position, size, delay (seconds), disposal method (none, keep, restore to background, restore to previous), transparent color number, local color count and data size.

How it works

It does not draw the GIF as an image; it reads the file's byte structure (header, color tables, extension blocks, frame blocks) to gather information. The frame data size is the number of compressed data bytes of each frame. Nothing is drawn, so even large GIFs are analyzed quickly.

Good to know

• GIF delays are in 1/100 second, shown here converted to seconds.
• The diagnosis is reference info pointing out common causes. Even with a problem listed, the GIF may play normally.
• To shrink it, reduce the size, frames or colors in the Trim and Resize GIF tool.
• Results are gone when you close the tab.