Dummy File Generator
Pick a size and an extension, and your browser writes the file — up to many gigabytes, with no upload and no server.
A real, openable PDF padded to the exact size you asked for.
This .pdf will be a real, openable file, at any size from 616 bytes.
Every byte is generated by your browser. Nothing is uploaded, and there is no server involved at any point.
About Dummy File Generator
Dummy File Generator makes test files of an exact size, in whatever extension you need — a 5 GB .iso to test an upload limit, a 100 MB .pdf that actually opens, a 2 GB .zip for a transfer test. Type a size, type an extension, and the bytes are generated by JavaScript in your own browser and written straight to the file you choose, so even multi-gigabyte files never sit in memory and nothing is ever uploaded. For common formats — PDF, ZIP, WAV, BMP and text formats like CSV, JSON, XML and HTML — the result is a genuinely valid file that opens in a normal application; for everything else you get random, incompressible bytes with the right extension and MIME type.
How to use Dummy File Generator
- Type a file name and the extension you need, or pick one of the presets.
- Enter the size and choose the unit — bytes through to terabytes.
- Choose the contents: a valid file for that extension, random bytes, zeros, or repeating text.
- Click Generate & download. In Chrome or Edge you pick where to save and the file streams to disk as it is created.
Frequently asked questions
- How do I create a large dummy file for testing?
- Enter the size you want, type the extension, and click Generate & download. The file is created by your browser and saved to your computer — no upload, no account and no size limit beyond your free disk space.
- Is the file really generated in my browser?
- Yes. Every byte is produced by JavaScript on your device. This site is a static export with no backend, so there is no server that could generate or receive a file.
- How large a file can I make?
- In Chrome or Edge on the desktop the file is streamed straight to disk as it is generated, so the only real limit is your free disk space — tens of gigabytes is fine. In browsers without the File System Access API (Firefox and Safari) the file has to be assembled in memory first, so keep it under about 2 GB.
- Will the generated PDF or ZIP actually open?
- Yes. Choose “Valid file for the extension” and PDF, ZIP, WAV, BMP and the text formats (TXT, CSV, JSON, XML, HTML, Markdown, SQL and more) are built with real headers and structure, padded to the exact size you asked for. Other extensions get random bytes with the correct extension and MIME type, which is what upload and transfer tests need.
- Is the file exactly the size I asked for?
- Yes — to the byte. You can also switch between 1 KB = 1,024 bytes (what Windows and macOS report) and 1 KB = 1,000 bytes (what drive manufacturers use).
- Should I use random bytes or zeros?
- Random bytes are incompressible, so the file keeps its size through gzip, ZIP and transfer compression — use them for upload and bandwidth tests. Zeros compress to almost nothing and are written faster, which suits disk-space and quota tests.
- Can I make a dummy file on my phone?
- Yes, but mobile browsers build the file in memory before saving it, so stick to smaller sizes — a few hundred megabytes at most.
- Does it work offline?
- Once the page has loaded, generation is entirely local, so it keeps working with no connection.