A 500 KB PNG test file

About this file

A 500 KB test file in PNG format, sized to exactly 512,000 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

500 KB is a realistic size for a single high-resolution photo. It puts a load close to real-world data on front-end image optimisation and preview-generation paths.

Base64-encoded it grows to roughly 667 KB, because Base64 inflates data by about 33%. If you embed files in data URIs, email attachments, or JSON payloads, your limits must account for that expansion.

Getting a feel for this size

On a 10 Mbps link the transfer takes roughly 410 ms, and about 41 ms at 100 Mbps. Base64-encoded it grows to roughly 667 KB.

Estimating a photographic PNG at roughly 2 bytes per pixel, this size works out to around 256,000 pixels — about 584 × 438 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