A 25 MB GIF test file

About this file

A 25 MB test file in GIF format, sized to exactly 26,214,400 bytes. Free to download with no signup, for verifying upload limits and file-handling behaviour.

The MD5, SHA-1 and SHA-256 values listed above are the real digests of this file. Recomputing them after download confirms the transfer was not corrupted, and they double as known-good expected values when testing a hashing library.

What this size means in practice

25 MB is widely known as the Gmail attachment limit. In practice, though, mail attachments are Base64-encoded and grow about 33%, so a 25 MB file becomes roughly 33 MB on the wire and usually will not send as-is.

That gap between the advertised limit and the post-encoding size is a pitfall every mail-sending feature eventually hits. Use this file to check whether your size validation runs before or after encoding.

Getting a feel for this size

On a 10 Mbps link the transfer takes roughly 21 seconds, and about 2.1 seconds at 100 Mbps. Base64-encoded it grows to roughly 34,133 KB.

Estimating a photographic GIF at roughly 0.5 bytes per pixel, this size works out to around 52,428,800 pixels — about 8,361 × 6,271 px at a 4:3 aspect ratio. Compression varies enormously with image content, so treat this purely as an order-of-magnitude figure.

What to check for this format

GIF begins with the ASCII signature GIF87a or GIF89a and uses a palette of up to 256 colours. Because it can hold multiple animation frames, code written for single-frame images either grabs only the first frame or, worse, expands every frame and consumes far more memory than expected.

• Whether resizing an animated GIF preserves the animation or flattens it to a still
• Whether thumbnail generation correctly extracts the first frame
• Whether you cap memory when expanding all frames — usage grows with frame count multiplied by resolution