Small things that do one job.
18 utilities I built while shipping apps. They run entirely in your browser: nothing uploads, nothing is stored, and there is no sign-up.
Build
Artwork and assets for shipping an app.
- Screenshot MockupFrame a screenshot for sharing — window chrome, backgrounds, 3D tilt and text layers.
- App Icon GeneratorA 1024×1024 PNG in; every iOS, iPadOS, macOS, watchOS and visionOS size out, as a ZIP.
- Favicon GeneratorOne square image in; every favicon PNG, the head snippet and site.webmanifest out.
Encode
Move data between representations, both ways.
Text
Compare, convert and render blocks of text.
- Markdown PreviewType markdown on one side, read it rendered on the other. Drop .md files to read them as one.
- Text DiffCompare two blocks of text line by line. Additions and removals are marked and counted.
- Case ConverterOne input, twelve naming conventions at once, with the token split that produced each one.
Network
Pull apart an address, a URL or a User-Agent.
- IP Subnet CalculatorDecode any IPv4 CIDR — network, broadcast, mask, wildcard, host range and total addresses.
- URL ParserSplit a URL into protocol, host, port, path, query and hash, every parameter decoded.
- User Agent ParserParse a User-Agent into browser, engine, OS and device — and see which rule matched.
Security
Random secrets, digests, and what is in a token.
- Password GeneratorCryptographically random passwords, drawn in the browser, with the entropy printed in bits.
- JWT DecoderReads a JWT header and payload and explains every registered claim. Never checks the signature.
- Hash GeneratorSHA-1, SHA-256, SHA-384 and SHA-512 of any text, all four at once, in hex or Base64. No MD5.
Electronics
Bench maths for hardware.
- Ohm's Law CalculatorSolve for voltage, current, resistance or power from any two known values.
- Resistor Color Code CalculatorDecode 4-band and 5-band color codes into resistance, tolerance and range.
- Voltage Divider CalculatorSolve any one of Vin, R1, R2 or Vout, with current, power and real E12/E24 parts.
The apps these came out of.
Utility software for macOS, iOS and the browser, built and shipped by one person. The tools above are the offcuts.