Developer Tools
These developer tools format, encode and generate common data formats entirely inside your browser. Nothing you paste is transmitted, which matters because the things people paste into online formatters are usually API responses and config files.
22 tools
- Markdown to HTML ConverterHeadings, lists, links, code and quotes — escaped properly.
- Time Zone ConverterOne instant, shown in every zone you care about.
- YAML to JSON ConverterFor the common subset — config files, not the whole spec.
- Roman Numeral ConverterBoth directions, with malformed numerals named.
- Subnet CalculatorNetwork, broadcast, usable range and host count.
- Data Size ConverterEvery unit at once, with the 1000 and 1024 split made explicit.
- Unix Timestamp ConverterEpoch seconds to a readable date, and back again.
- Regex TesterSee every match and capture group, safely.
- Text DiffLine-by-line differences, computed in your browser.
- Cron Expression ExplainerWhat a schedule actually means, in a sentence.
- Query String ParserBreak a URL into readable parameters, decoded.
- Number Base ConverterConvert between bases, one number per line.
- JSON FormatterIndent, validate and sort JSON, with errors that say where.
- Base64 Encoder & DecoderEncode or decode Base64, including the URL-safe variant.
- URL Encoder & DecoderPercent-encode a value, or read back one that has been mangled.
- UUID GeneratorCryptographically random v4 UUIDs, as many as you need.
- SHA-256 Hash GeneratorHash text to SHA-256 or CRC-32, computed in your browser.
- CSV to JSON ConverterConvert CSV to JSON, handling quoted commas properly.
- Password GeneratorCryptographically random passwords, generated on your device.
- JWT DecoderRead a token’s header and claims, entirely in your browser.
- HTML Encoder & DecoderEscape text for HTML, or decode entities back to characters.
- Color ConverterConvert between colour notations, with contrast ratios.
About developer tools
Every tool in this category is a pure function over a string, which is why none of them need a server and why pasting into one that does is an unnecessary risk. The things developers paste into online formatters are, overwhelmingly, the things they should be most careful with: API responses carrying bearer tokens, configuration files with connection strings, JWTs whose payload identifies a user, log excerpts containing customer data. A formatter that uploads that to be pretty-printed has taken a copy of it, and the retention policy governing that copy is somebody else's. Running the transform in the page removes the question entirely — there is nothing to retain because nothing was sent. The other thing worth knowing about this category is that the transforms are exactly specified, so correctness is checkable rather than a matter of trust. JSON has a published grammar; Base64 has an RFC; SHA-256 has official test vectors, which is what the implementation here is verified against. Where a tool here differs from another, one of them is wrong, and it is usually about Unicode: naive Base64 implementations operate on bytes and corrupt anything outside basic Latin, and naive slug generators strip accented letters instead of folding them.
Every tool runs entirely in your browser. Your files are never uploaded to a server.