Dev calculators
Encoders, decoders, formatters, validators. The kind of one-off utility every engineer reaches for.
All dev tools
14 tools, each runs locally in your browser. Click any card to open it.
AES Text Encryptor / Decryptor takes token quantity, price, fees, holding period and returns the matching aes text enc…
Aesthetic Symbols takes source text, target style, optional rules and returns the matching aesthetic symbols result. R…
Base64 Encoder / Decoder takes source value and source unit and returns the matching base64 encoder / decoder result. …
Base64 Image Viewer takes source value and source unit and returns the matching base64 image viewer result. Runs entir…
CSS Formatter takes string, regex, format, count and returns the matching css formatter result. Runs entirely in your …
CSS Minifier takes string, regex, format, count and returns the matching css minifier result. Runs entirely in your br…
HTML Entity Encoder / Decoder takes string, regex, format, count and returns the matching html entity encoder / decode…
JSON Formatter / Validator takes string, regex, format, count and returns the matching json formatter / validator resu…
JSON to CSV Converter takes source value and source unit and returns the matching json to csv result. Runs entirely in…
JSON to XML Converter takes string, regex, format, count and returns the matching json to xml result. Runs entirely in…
JWT Decoder takes token quantity, price, fees, holding period and returns the matching jwt decoder result. Runs entire…
Regex Tester takes string, regex, format, count and returns the matching regex tester result. Runs entirely in your br…
Unix Timestamp Converter takes string, regex, format, count and returns the matching unix timestamp result. Runs entir…
URL Encoder / Decoder takes string, regex, format, count and returns the matching url encoder / decoder result. Runs e…
About dev
Developer utility calculators cover the daily reach-for-it tools: Base64 encode/decode, URL encode/decode, JSON format and validate, JSON to CSV, regex tester with capture-group highlighting, hash generation (MD5, SHA-1, SHA-256, SHA-512), UUID v4 generator, IP subnet calculator (CIDR notation, IP range, broadcast, network address), color conversion (HEX, RGB, HSL, OKLCH), Unix timestamp <-> ISO 8601, and JWT decoder (read-only, no signing).
Use these tools when you need to verify a JSON payload from an API, decode a Base64-encoded auth token, plan a /24 subnet split, generate a SHA-256 of a file for integrity checking, decode a JWT to inspect claims during debugging, or convert HSL design tokens to HEX for a CSS variable.
Sources: RFC standards (RFC 4648 Base64, RFC 4122 UUID, RFC 8259 JSON, RFC 7519 JWT), WHATWG URL spec, W3C CSS Color spec. Everything runs client-side; sensitive payloads (tokens, secrets) never leave your browser.
Common use cases
Real scenarios where the dev calculators in this category earn their keep.
Decode a Base64 auth token
Paste the encoded string, get the decoded payload. Round-trip in either direction. Handles standard and URL-safe Base64 variants.
Format and validate JSON
Paste compressed JSON, get pretty-printed output with syntax highlighting. Error messages point at the line + column of the first parse failure.
Subnet a /24 into /28s
CIDR calculator shows network address, broadcast, usable host range, and total host count for any prefix length. Subnet a parent into smaller children.
Test a regex with named groups
Paste a pattern and a test string. The tool highlights each match and lists capture-group values with positions. JavaScript regex flavor by default; PCRE toggle.
Decode a JWT to inspect claims
Paste a JWT (header.payload.signature). The tool decodes Base64 of the first two segments and displays the JSON. Does NOT verify the signature.
Key terms
Glossary for the formulas and conventions these tools use.
- Base64
- Binary-to-text encoding using 64 ASCII characters. URL-safe variant swaps + and / for - and _. Pads with = to a multiple of 4 chars.
- CIDR
- Classless Inter-Domain Routing. /24 = 256 addresses, /28 = 16 addresses, /16 = 65,536 addresses. Used for IPv4 and IPv6 subnetting.
- UUID v4
- Universally Unique Identifier, random-generated. 128 bits, 36 chars with hyphens. Collision probability negligible (~10^-37 for 1 billion UUIDs).
- SHA-256
- Secure Hash Algorithm 2. Produces a 256-bit fingerprint. Industry standard for file integrity and signing. Not reversible.
- JWT
- JSON Web Token. Three Base64-encoded segments separated by periods: header, payload, signature. Signature verifies authenticity.
- OKLCH
- Perceptually-uniform color space (L = lightness, C = chroma, H = hue). Used in modern CSS for predictable color manipulation.
- ISO 8601 timestamp
- Standard date-time format: YYYY-MM-DDTHH:MM:SSZ (Z = UTC) or with +HH:MM offset. Sortable as a string.
Frequently asked questions
Short answers to the most common dev questions.