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
3 tools- Screenshot MockupDrop a screenshot and export a framed, share-ready image — window chrome, backgrounds, 3D tilt and text layers.
- App Icon GeneratorDrop a 1024×1024 PNG and get every iOS, iPadOS, macOS, watchOS and visionOS icon size back as a ZIP.
- Favicon GeneratorOne square image in; the 16, 32, 48, 180, 192 and 512 PNGs, the head snippet and site.webmanifest out.
Encode
3 toolsText
3 tools- Markdown PreviewType markdown on one side and read it rendered on the other. Drop .md files to read several as one continuous document.
- Text DiffCompare two blocks of text line by line. Added and removed lines are marked and counted, with ignore-case and ignore-whitespace options.
- Case ConverterOne input, twelve naming conventions at once, with the token split that produced each one.
Network
3 tools- 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, and read every parameter raw and decoded.
- User Agent ParserParse a User-Agent into browser, engine, OS and device — and see which rule matched.
Security
3 tools- Password GeneratorCryptographically random passwords, drawn in the browser, with the entropy printed in bits.
- JWT DecoderDecodes a JWT header and payload and explains every registered claim. Decode only — the signature is never checked.
- Hash GeneratorSHA-1, SHA-256, SHA-384 and SHA-512 of any text, all four at once, in hex or Base64. No MD5 — Web Crypto does not implement it.
Electronics
3 tools- 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 per resistor, real E12/E24 parts and the loaded output.
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.