A 50 MB PNG test file

About this file

A 50 MB test file in PNG format, sized to exactly 52,428,800 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

50 MB is the point where GitHub starts warning you on push (it hard-rejects above 100 MB). In practice it is the decision line for whether a binary belongs in Git directly or should move to Git LFS.

At this scale, an implementation that buffers the whole request in memory burns 50 MB or more per worker process — ten concurrent uploads means 500 MB. It is a good size for verifying that streaming or spill-to-temp-file actually works.

Getting a feel for this size

On a 10 Mbps link the transfer takes roughly 41.9 seconds, and about 4.2 seconds at 100 Mbps. Base64-encoded it grows to roughly 68,267 KB.

Estimating a photographic PNG at roughly 2 bytes per pixel, this size works out to around 26,214,400 pixels — about 5,912 × 4,434 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

PNG is lossless and carries an alpha channel. Every file starts with the fixed 8-byte signature 89 50 4E 47 0D 0A 1A 0A, followed by IHDR / IDAT / IEND chunks. The key question for upload validation is whether your code identifies the file by those leading bytes rather than by its extension.

• Whether the alpha channel survives resize and conversion — converting to JPEG destroys it
• Whether image libraries such as GD, ImageMagick, or sharp hit their memory ceiling — PNG memory use scales with decoded pixel count, not file size
• Whether metadata such as tEXt chunks is stripped — PNG has no EXIF, but text chunks can retain information