Stress Test Data Generator: 1 KB to 10 MB

Generate stress-test data by exact byte size

Unlike the other repeaters that count repetitions, this tool generates output to an exact byte size — 1 KB, 10 KB, 100 KB, 1 MB, or 10 MB. Useful when you're testing:

Form field length limits: Submit 1 MB of text into a textarea to see what breaks.
Database column sizes: Test what happens when a TEXT column gets exactly 10 KB of input.
Upload size limits: Generate a 10 MB .txt file to test against Nginx's client_max_body_size or similar.
Memory benchmarks: Profile parsers or string-handling code with predictably-sized input.
API payload limits: Hit your API with a known-size JSON body to check rate limits and timeout behavior.

Three output variants

Exact size: Pattern repeated until the target byte count is reached, then truncated. Pure string of bytes.
Line-broken: Pattern repeated into 80-character lines with newlines between. Useful when you need readable test data.
Numbered lines: Each line prefixed with 1., 2., etc. Useful for debugging which line caused a failure.

Note on UTF-8 encoding

For pure ASCII patterns ("qwerty", numbers, English letters), the byte size equals the character size. If you use multi-byte characters (emojis, accented characters, CJK), the actual byte size in UTF-8 will be larger than the displayed character count. For accurate byte sizes, stick with ASCII.

Common questions

Frequently asked.

Sometimes you just need a known-size file to upload, paste, or send via API — without writing a one-off script. This tool is faster than spinning up a Python REPL for a one-time task.

Exactly 1 MB (1,048,576 bytes for ASCII patterns). The tool pads or truncates the final repetition to hit the target size precisely.

10 MB. Beyond that, browser memory and clipboard handling become unreliable. For larger test data, generate the file with a script: python -c "print('a' * 100000000)" > test.txt

Most modern browsers handle 10 MB clipboard writes, but it can be slow. For large outputs, use the Download button instead — it streams directly to a file without going through the clipboard.

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Stress test data, any size.