Create a 100 MB or 1 GB test file of zeros or random bytes in the browser
Processed in your browser. Nothing is uploaded. Updated on 24 Oct 2026.Create a large file for testing transfer speed, an upload limit or free disk space, up to 1 GB, without fsutil or mkfile. Zeros compress to almost nothing, so a link or a zip may make a 1 GB file look fast; random bytes do not compress, which makes them the honest choice for speed tests. On Chrome and Edge on a computer the file is written straight to the place you choose, so even 1 GB needs little memory.
The page opens on BIN at 100 MB; tap 1 GB or type the size you need.
Choose Zeros, or Random bytes when the test must not be helped by compression.
Press Make file. On Chrome or Edge on a computer, pick where to save it and it is written straight there.
The Dummy File Generator makes a file of exactly the size you ask for, so you can check what an upload form, an email server or an API does at its limit. Ask for 5 MB and you get 5,242,880 bytes, not "about 5 MB". KB, MB and GB here count in 1,024s, as Windows and most upload limits do; under More options you can switch to 1,000s.
| Type | What is inside | Smallest size |
|---|---|---|
| TXT | One readable line, repeated | 1 byte |
| BIN | Zeros, or random bytes | 1 byte |
| CSV | A header and numbered rows of Test Users at example.com | 65 bytes |
| One A4 page saying it is a dummy; padding in a stream no page draws | 850 bytes | |
| JPG | A 16 x 16 grey image; padding in comment segments | 163 bytes |
| PNG | A 16 x 16 grey image; padding in a text chunk | 360 bytes |
| ZIP | One uncompressed entry, dummy.txt | 116 bytes |
Zeros compress to almost nothing, so a transfer or a zip can make them look faster than real data. Random bytes come from your browser's cryptographic source and do not compress, which makes them the fair choice for speed tests.
The rest of the article, and all 6 questions about Dummy File Generator, are on the Dummy File Generator page.
Choose a type such as PDF or TXT, tap a common size like 1 MB or type any size in bytes, KB, MB or GB, and press Make file. The file is written on your device and is exactly the size asked for, down to the byte, up to 1 GB.
A TXT or BIN file can be 1 byte. A ZIP needs 116 bytes, a JPG 163, a PNG 360 and a PDF 850, because each format has a fixed structure before any padding. A CSV needs 65 bytes for its header and one row. Smaller sizes are refused with the minimum stated.
Usually yes. The file is written to disk in 8 MB pieces as it is made, either to the place you choose or to the browser's private storage, so memory use stays small. A phone needs 1 GB of free space, and the progress bar and Cancel button stay on screen.
A video padded to size would not play as a video, so offering one would make an upload test pass for the wrong reason. To test a video upload, record a short clip with your phone and trim or join it to the size you need with the video tools on this site.
Still stuck? Ask about Dummy File Generator and anybody who knows can answer. No account needed.
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