Overview
Introduction
Some tests specifically need binary data, not text, to confirm that an upload form, transfer script, or compression tool behaves correctly on non-textual content.
This tool generates that data instantly and lets you download it as a .bin file.
What Is Binary File Generator?
A random binary file generator that fills a byte array with cryptographically random values and offers it for download, alongside a hex dump so you can see the actual bytes without opening the file elsewhere.
Everything happens locally in your browser; no data is generated on or sent to a server.
How Binary File Generator Works
A Uint8Array of the requested size is filled using crypto.getRandomValues(), the same secure randomness source browsers use for generating cryptographic keys and tokens.
The raw bytes are offered for download as a Blob with an application/octet-stream MIME type, while a separate hex-encoded string (two hex digits per byte, space-separated) is rendered for a quick visual preview.
When To Use Binary File Generator
Use it when you need incompressible, non-textual test data: confirming an upload accepts arbitrary binary content, benchmarking a compression tool against data that shouldn't compress well, or generating a throwaway file to test transfer speed.
It's also useful for filling a file with unpredictable content when you specifically don't want structured or guessable bytes.
Often used alongside Text File Generator, String to Hex Converter and Empty File Generator.
Features
Advantages
- Uses a cryptographically secure random source rather than a predictable pseudo-random generator.
- Instant, local generation with a live hex preview.
- Simple, adjustable size control.
Limitations
- Capped at 65,536 bytes per generation due to the browser's crypto.getRandomValues() limit.
- The hex preview becomes unwieldy to read at larger sizes; it's meant as a spot-check, not a full hex editor.
Examples
Best Practices & Notes
Best Practices
- Keep the size close to what you actually need to test, since larger files take longer to render as a hex preview.
- Use Convert Hex to a String if you need to inspect a specific byte range as text.
- Combine with Generate an Empty File when you need both a zero-byte and a random-content test case.
Developer Notes
Downloading passes the Uint8Array directly to the Blob constructor rather than converting it to a JavaScript string first, since round-tripping arbitrary byte values through a UTF-16 string and back would corrupt any byte above 0x7F.
Binary File Generator Use Cases
- Testing that an upload form accepts arbitrary binary files
- Benchmarking compression or transfer tools against incompressible data
- Generating a throwaway file with unpredictable content
Common Mistakes
- Assuming the hex preview is an efficient way to inspect large files; it's meant for a quick spot-check, not full analysis.
- Requesting more than 65,536 bytes in one generation; the browser's random source can't fill that in a single call.
Tips
- If you need a much larger binary file, generate this one repeatedly and concatenate the downloads with a local tool.
- The hex preview format matches what Convert Hex to a String and Convert a String to Hex expect, so you can copy a slice directly between them.