Developer tools
Inspect URLs and network addresses, create hashes and IDs, work with JWT signatures and generate CSS.
29 tools in this category. Every tool runs in the browser and needs no sign-up.
HTTP Headers to JSON
Parse HTTP header lines into JSON arrays while preserving repeated header names.
Cookie Parser
Parse a request Cookie header. Keep duplicate names and optionally decode percent escapes.
UTM Campaign URL Builder
Build campaign links with source, medium and campaign. Preserve other query parameters and fragments.
robots.txt Generator
Generate one User-agent group with Allow, Disallow and an optional sitemap. Rules do not provide access control.
HTML Meta Tag Generator
Generate escaped title, description, canonical and Open Graph tags. Optional URLs must use HTTP or HTTPS.
Chmod Permission Calculator
Convert three-digit octal permissions and nine-character rwx notation. Special permission bits are not supported.
IPv4 Range to CIDR
Cover inclusive start and end IPv4 addresses with the smallest aligned CIDR blocks, without extra addresses.
Number Base Converter
Convert integers between bases 2 through 36, including binary, octal, decimal and hexadecimal, without precision loss.
HEX / RGB / HSL Converter
Convert a CSS color from HEX, RGB or HSL to all three formats and preview the resulting color.
UUID v4 Generator
Generate 1 to 100 random UUID version 4 identifiers using the browser cryptographic random generator.
URL Parser
Split an absolute URL into protocol, host, port, path, query parameters and fragment. Preserve repeated query parameter names.
IPv4 and Integer Converter
Convert dotted IPv4 addresses to unsigned 32-bit integers and back.
IPv4 Subnet Calculator
Calculate network, netmask, host range and address counts from IPv4 CIDR.
IPv6 Expand / Compress
Expand IPv6 into eight groups or compress its longest zero run.
CIDR and Netmask Converter
Convert an IPv4 prefix length into a dotted netmask and back.
JWT Generator and Signer
Create signed JWTs with HMAC, RSA, RSA-PSS or ECDSA using browser Web Crypto.
JWT Signature Verifier
Verify a JWT signature against an explicitly selected algorithm and trusted key.
JWT Claims Checker
Check exp, nbf, iat, issuer and audience against an explicit reference time and leeway.
URL Builder
Build an HTTP or HTTPS URL from a base, JSON query values and a fragment.
Extract URL Slug
Extract and percent-decode the last nonempty path segment of an absolute URL.
UUID Inspector
Inspect UUID text for its version, variant, nil and max values.
Color Contrast Checker
Calculate WCAG 2 contrast for two opaque sRGB HEX colors and check AA/AAA text thresholds.
PX / REM Converter
Convert pixels and rem units using an explicit root font size.
CSS Clamp Generator
Generate a fluid CSS clamp between two sizes and viewport widths.
Cadence → Go
Convert Cadence workflow descriptions to Go code for execution in Go environments.
QR Code Generator
Create custom QR codes for free. Generate QR codes easily in seconds.
QR code scanner
Read a QR code from a screenshot or photo: upload, drag in or paste an image. The code is decoded in your browser and links are never opened automatically.
Barcode generator
Create EAN-13, EAN-8, UPC-A, Code 128, Code 39, ITF-14 and Codabar barcodes. Check digits are added or verified; download a sharp PNG or SVG.
Regex tester
Test JavaScript regular expressions online: live match highlighting, capture and named groups, all flags and a replace preview. Slow patterns stop after 1s.