Generate test files of any size
Produce a file of arbitrary size up to 100 MB filled with zeros, crypto-random bytes, lorem ipsum, or a custom repeating pattern. Useful for upload limits, throughput tests, and storage QA.
Will generate: 1.00 MB
Click Generate & download to save the file. Generation happens entirely in your browser.
How to make a test file
Pick a size, choose a fill mode, and download. Random uses crypto-grade bytes; pattern repeats your string; ascii fills with lorem ipsum.
- 01
Pick size
Type a number and pick B, KB, or MB.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
sizeinpututf-8client-sidevalidatedsize · text1 MB · set1,048,576 bytes
loaded · parsedclient-side - 02
Choose fill
Zeros for sparse, random for incompressible, ascii for human-readable.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
filloptionslivememoisedtogglesfill · memoisedrandom · livecrypto bytes
options set · memoisedlive - 03
Name it
Filename + extension hint MIME and downstream parsers.
Randomness — where used — comes from
crypto.getRandomValues, neverMath.random. Heavy work sits inuseMemo.namecomputeinstantlocaldeterministicname · instantbin · computedtest-file.bin
computed · instantinstant - 04
Generate
One click — the file lands in your Downloads folder.
Copy writes through
navigator.clipboardand downloads use aBlob— zero network traffic. Same input plus same options always yield the same bytes.savecopydownloadzero-networkreproducibleok · copiedready · copiedDownloaded
shipped · ready to shipsuccess
Pro tips for everyday utilities
Reach for crypto.getRandomValues
Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.
Mock data with seeds
Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.
Reference cards beat memory
Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.
Browser APIs vary
Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.
Persist in the right place
localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.
When to make test files
Upload limits, throughput, storage QA.
Upload limits
Probe app/server file-size caps deliberately. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.
CSPRNG-backedThroughput tests
Measure transfer speed with known payloads. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.
reproducibleStorage QA
Fill a disk to test low-disk handling. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.
snappyBackup smoke tests
Create files of known shape to verify backups. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.
feature-detectedCompression bench
Random vs zeros to measure gzip ratios. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.
deterministicHash demos
Pair with checksum verifier for teaching. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.
production-readyFrequently asked questions
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