Test File Generator

What it's for

Make a file of exactly the size you ask for, or a set of files that add up to a total, without hunting for real files of the right size. The contents are filler: zeros, random bytes, or a line of text repeated.

For example, when an upload page is slow with large batches, make 100 MB as one file and as a hundred 1 MB files, then time both to see whether the size or the number of files is the problem.

How to use it

Set Total size and its Unit, then choose Make:

• One file saves a single file of that size, named as in File name.
• Several files (ZIP) cuts the total into files of the Each file size, the last one smaller if it doesn’t divide exactly, and saves them in a ZIP. A counter goes before the extension: test-01.bin, test-02.bin…

KB, MB and GB are powers of 1,000 (1 MB is 1,000,000 bytes), as file managers on the Mac and most upload limits count them; KiB, MiB and GiB are powers of 1,024 (1 MiB is 1,048,576 bytes), as Windows counts them while calling them KB and MB. Fill with zeros, random bytes (which don’t compress, so they test real transfer sizes), or text you type, repeated end to end. Every setting is remembered in this browser.

Example

Set Total size to 2.5, Unit to MB, Make to Several files (ZIP) and Each file to 1 MB, then Make and save. The message reads:

Saved 3 files (test-01.bin to test-03.bin), 2,500,000 bytes in all, in a ZIP.

The ZIP, test.zip, holds two files of 1,000,000 bytes and one of 500,000.

Good to know

The files are made in this browser’s memory before saving, so very large sizes (several GB) may fail or slow the computer down. A ZIP made here holds files as they are, without compression, and must be under 4 GiB in all; a set is limited to 10,000 files. Files filled with zeros or text compress to almost nothing, so a server or connection that compresses will move far less data than the size suggests: use random bytes to avoid that. The name and extension don’t change the contents, so a file called test.pdf isn’t a real PDF.