Dummy File Generator
Generate a test file of an exact size in KB, MB, KiB or MiB, filled with random bytes, zeros, text or CSV rows, and download it straight from your browser.
Free · No sign-up · Your inputs stay in your browser
Input
Generate a dummy file of any size
Output
9.54 MiB
Linux / macOS
head -c 10000000 /dev/urandom > dummy.bin truncate -s 10000000 sparse.bin # instant, takes no disk space fallocate -l 10000000 filled.bin # instant, really allocated (Linux)
Windows
fsutil file createnew dummy.bin 10000000
For testing upload limits (Nginx client_max_body_size, PHP upload_max_filesize and post_max_size), progress bars and storage quotas. Random bytes are the honest test for anything that compresses on the way, since a file of zeros shrinks to a few kilobytes under gzip. Capped at 512 MiB in the browser; on a server, the commands below have no limit.
Runs in this browser. Nothing you paste is sent to a server.
About this tool
Method, assumptions, practical next steps, and limits.
Testing upload limits
An upload passes through several limits: Nginx's client_max_body_size, PHP's upload_max_filesize and post_max_size, the framework's validation rule, a CDN or load balancer body limit and the storage quota. Files just under and just over each one show which layer rejects a request and what error the user sees.
Random versus zeros
Gzip and Brotli compress a file of zeros to almost nothing, so it does not exercise bandwidth or storage the way a real file does. Random bytes do not compress, which makes them the honest test for anything compressed in transit.