Developer Tools
55 free online calculators — instant results, no sign-up
All 55 Developer Tools Tools
CPU Cooler Calculator
TDP headroom to air/AIO tierTapping Drill Size Calculator
Nominal minus pitch by materialIPv6 Formatter
RFC 5952 expand & compressGuitar Capo Transposer
chord sequence · semitone shift per fretBase Converter for Developers
Binary, octal, decimal, hex — batch conversionColor Code Converter
HEX, RGB, HSL and CMYKJSON Formatter
Beautify, minify and validate JSONBase64 Encoder / Decoder
Encode and decode Base64 textURL Encoder / Decoder
encodeURI and decodeURI onlineUnix Timestamp Converter
Timestamp ↔ date conversionRegex Tester
Test regular expressions with match highlightingHash Calculator
MD5 and SHA-256 hashing onlineCharacter Counter
Words, characters, lines and bytesLorem Ipsum Generator
Placeholder text with custom paragraph countMarkdown Preview
Live rendering with syntax highlightingNEWText Diff Tool
Line-by-line comparison with highlighted changesNEWHTML Entities Converter
Characters ↔ HTML entity codesUUID Generator
Batch UUID v4 generation with multiple formatsQR Code Generator
Text, links and WiFi to QR code with PNG downloadCron Expression Parser
Human-readable meaning and next 10 run timesSubnet Calculator
IP/CIDR to mask, broadcast and usable hostsChmod Calculator
rwx checkboxes to octal and symbolic notationCase Converter
camelCase, snake_case, kebab-case and 7 more stylesUnicode Code Point Lookup
Character to U+ code point, UTF-8 bytes and HTMLJWT Decoder
Decode header/payload, inspect claims and expirypx ↔ rem Converter
Root font-size based conversion with common scale tableASCII Code Table
Char ↔ code in dec/hex/oct with full printable tableDownload Time Calculator
File size over bandwidth to transfer durationUptime SLA Calculator
Availability percentage to allowed downtime per yearAspect Ratio Calculator
Simplify ratios and scale dimensions proportionallyCSV ↔ JSON Converter
Two-way conversion, RFC 4180 quote escapingColor Contrast Checker
WCAG AA/AAA ratios via relative luminanceText Line Tools
Dedupe, sort, trim, remove empty and number linesURL Slug Generator
Title → lowercase hyphenated slug, accents strippedMorse Code Translator
Text to Morse, audio playback, reference chartHTTP Status Codes
1xx-5xx lookup by category with meaningsBitwise Calculator
AND/OR/XOR, shifts, bit visualizationIEEE 754 Analyzer
Float32/64 bit layout and precisionURL Parser
Split protocol/host/query paramsCommon Port Reference
40+ ports, searchableMeta Tag Generator
OG/Twitter tags, one-click copyOpen Source License Picker
Comparison table, wizard recommendationEAN-13 Barcode Tool
Checksum validate & generate, prefix tableSQL Formatter
Uppercase keywords, indent, minifyMojibake Fixer
latin1/GBK/UTF-8 fix, hex decodeYAML ↔ JSON Converter
Two-way with line-numbered errorsJSON to TypeScript
Generate interfaces from JSONAES Encryption Tool
AES-256-GCM/CBC, local PBKDF2XML Formatter
Beautify/minify + tag validationHMAC Generator
HMAC-SHA family + Hex/Base64robots.txt Generator
UA rules + AI bots + SitemapChinese ID Card Validator
GB11643 checksum + region parsingUser-Agent Parser
Browser/OS/device · bot detectionTraditional-Simplified Converter
Chinese char + word-level mappingUTM Link Builder
Campaign URL tagging · presets · copyRelated Guides
Number Bases for Developers: Binary, Hex & Octal
Binary (0b), octal (0o), hex (0x) — hex is binary compressed 4 bits per digit: 0b1010 = 0xA = 10. 0xFF = 255, 0x100 = 256. Colors #RRGGBB are three hex bytes. Includes fast conversion, bit operations and the 0x7FFFFFFF landmarks.
Color Codes: HEX, RGB, HSL & Conversion Guide
HEX #3B82F6 = RGB(59,130,246) — each hex pair is one channel ÷ 255. HSL separates hue (0-360° wheel), saturation, lightness — best for building palettes: same hue, vary L for shades. Includes conversion math, alpha channels and contrast ratios.
JSON Formatting: Syntax Rules, Validation & Fixes
JSON: double-quoted strings only, no trailing commas, no comments, no undefined. Top causes of parse errors: single quotes, trailing comma, unquoted keys. Includes the type system, pretty-print conventions, JSONC/JSON5 escapes and debugging workflow.
Base64 Encoding: How It Works & When to Use It
Base64 packs 3 bytes into 4 ASCII chars (A-Z, a-z, 0-9, +, /) — +33% size, universally safe through text channels. Padding "=" marks the remainder. NOT encryption — trivially reversible. Uses: data URIs, email attachments, API tokens. URL-safe variant swaps +/ to −_.
URL Encoding: Percent-Encoding Rules & Examples
URL encoding replaces unsafe bytes with %XX hex: space → %20 (or + in query strings), 中 → %E4%B8%AD (UTF-8 bytes). Reserved chars: / ? & = # %. encodeURIComponent for parameters, encodeURI for whole URLs — the difference matters. Full table inside.
Unix Timestamps: Seconds, Milliseconds & Conversion
Unix timestamp = seconds since 1970-01-01 00:00:00 UTC. 1735689600 = 2025-01-01 00:00 UTC. Milliseconds version ×1,000 (JS default). Includes the 13-vs-10 digit check, timezone independence, the 2038 problem and language conversion snippets.