Developer Toolbox

Free online developer tools from cfgnotes — JSON formatter, YAML converter, JWT decoder, regex tester, hash generator, Base64 encoder, cron parser, CIDR calculator, QR code generator and 20+ more utilities. All data is processed locally in your browser — nothing is uploaded to any server. Perfect for daily development and DevOps debugging.

JSON Formatter

Format, minify, validate and highlight JSON with syntax error detection and one-click copy.

Format · Validate

URL Encode / Decode

Encode and decode URL special characters, supporting full URLs or individual parameters.

URL · Encoding

Base64 Encode / Decode

Convert between plain text and Base64 with UTF-8 support. Works with URLs, images and certificates.

Encode · Decode

Timestamp Converter

Convert between Unix timestamps and human-readable dates. Supports seconds and milliseconds with live current timestamp.

Time · Convert

Regex Tester

Test regular expressions with g/i/m/s flags, highlighted matches and optional replacement preview.

CSV ↔ JSON

Convert between header-row CSV and JSON arrays with quoted field support.

YAML ↔ JSON

Convert between YAML and JSON with validation and error messages (uses js-yaml CDN).

Config · Convert

Text Diff

Compare two texts line by line with added/removed line highlighting (uses diff CDN).

Line Tools

Sort, deduplicate, remove blank lines, trim whitespace, reverse and count lines/characters.

QR Code Generator

Render URLs or any text as a QR code canvas with PNG download support.

QR Code · Canvas

Password Generator

Generate secure random passwords with configurable length and character sets. Optionally exclude ambiguous characters.

Random · Security

Hash Generator

Generate MD5, SHA-1, SHA-256 and other hash values for password verification and integrity checks.

Crypto · Verify

Cron Expression Parser

Parse 5-field cron expressions and preview upcoming trigger times on a timeline (standard UNIX semantics).

Schedule · Cron

UUID / ULID Generator

Batch generate UUID v4, ULID-compliant 26-character IDs, and Nano-style random strings.

Storage Unit Converter

Convert between Bytes, KB, MB, GB, TB, PB and more. Supports binary (1024) and decimal (1000) modes.

Storage · Convert

HTML Entities

Encode or decode HTML character entities (&, <, etc.).

JWT Decoder

Parse JWT Header and Payload (Base64URL + JSON). Does not verify signatures.

Case Converter

One-click conversion between camelCase, PascalCase, snake_case, kebab-case and CONSTANT_CASE.

Variable · Naming

Color / Contrast

Convert between HEX, RGB and HSL with WCAG contrast ratio calculation.

CIDR Calculator

Calculate network address, broadcast and available hosts from IPv4 prefix.

Network · IPv4