Network

Convert any MAC address into its modified EUI-64 interface ID and the matching IPv6 link-local address — the same form Windows / Linux compute automatically.

Build URLs by combining a base address with editable key-value query parameters — each pair toggleable, properly percent-encoded.

Type an IPv4 or IPv6 address and see its class, scope (private / public / loopback / link-local), decimal value, binary, reverse-DNS notation, and /32 CIDR.

Searchable cheat sheet for ~60 standard TCP / UDP port numbers — from 22 (SSH) and 80 (HTTP) to 6379 (Redis) and 27017 (MongoDB).

Searchable cheat sheet for DNS record types — A, AAAA, CNAME, MX, TXT, NS, SOA, PTR, SRV, CAA, DNSSEC, SVCB / HTTPS — with examples.

Parse an IPv4 CIDR into network address, broadcast, netmask, wildcard, host range, and class. Shows binary breakdown and private/public status.

Parse a User-Agent string into browser, engine, OS, device, and CPU. Detects 20+ bots including GPTBot, ClaudeBot, PerplexityBot.

Searchable list of every HTTP status code (1xx-5xx) with summary, RFC, when to use, and common pitfalls.

Generate Certificate Authority Authorization (CAA) DNS records so only the CAs you trust can issue TLS certificates for your domain. Builds BIND-format records and split tag/value rows for control-panel UIs, plus a one-click list of common CAs (Let's Encrypt, DigiCert, Google, Amazon, …).

Coalesce a messy list of IPv4/IPv6 addresses, CIDR blocks, and ranges into the smallest equivalent set of CIDR prefixes.

Searchable catalog of well-known URIs registered with IANA — `security.txt`, `openid-configuration`, `apple-app-site-association`, `acme-challenge`, and 30+ more, with RFC references and use cases.

Generate code_verifier + S256/plain code_challenge for OAuth 2.0 PKCE (RFC 7636). Also builds the authorization URL and a ready-to-paste curl for the token exchange.

Estimate download time from file size and connection speed — or the speed required to transfer a given size within a deadline. Includes TCP/overhead and presets for common connections.

Build or parse a DKIM (DomainKeys Identified Mail) DNS TXT record — paste your public key, pick selector, key type (RSA/Ed25519), hash and flags, get the full record plus the selector._domainkey hostname and a DNS-chunked version for records over 255 chars.

Paste or load a sitemap.xml (or a sitemap-index .xml) and instantly see URL count, size, spec compliance, and distributions of changefreq, priority and host — entirely in your browser.

Paste any IANA cipher suite name like TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 and get a breakdown into key exchange, authentication, bulk cipher, mode, and MAC — plus a security grade covering forward secrecy, AEAD, hash strength, and known-broken algorithms.

Build a mailto: URL with To, Cc, Bcc, subject, and body — RFC 6068 percent-encoded, ready to drop into an <a> tag.

Paste a robots.txt and a list of (user-agent, path) pairs to see exactly which line allows or blocks each — with longest-match precedence, wildcards, and the * group fallback.

Compute the sha256 / sha384 / sha512 base64 hash an inline <script> or <style> block needs to be whitelisted by a Content-Security-Policy.

Compose a Strict-Transport-Security header — max-age, includeSubDomains, preload — with a live preload-list eligibility check.

Compose a Sender Policy Framework TXT record from mechanisms, IPs and includes — with a live DNS-lookup counter and warnings.

Compose a `_dmarc` TXT record — policy, subdomain policy, percentage rollout, alignment, rua/ruf reporting — with safety warnings.

Compose a `Set-Cookie` response header from name/value plus the security attributes — SameSite, Secure, HttpOnly, Partitioned, Max-Age — with safety warnings.

Strip `utm_*`, `fbclid`, `gclid` and 30+ other tracking params from a URL — paste, get a clean shareable link back.

Encode `username:password` into the Base64 `Authorization: Basic` header — or paste an existing header back to see who's in it.

Build the `Permissions-Policy` response header — toggle camera, microphone, geolocation, payment, fullscreen and 20+ other browser features by origin allowlist.

Pick a Referrer-Policy value and see exactly what `Referer` header outbound requests will send — same-origin, cross-origin HTTPS, HTTPS→HTTP downgrade.

Split a long SPF, DKIM or DMARC TXT record into the 255-byte chunks the DNS protocol requires — outputs BIND, generic zone file, Cloudflare or Route 53 syntax.

Expand a CIDR block (10.0.0.0/24) into a list of IPs, or convert a start-end range into the smallest covering CIDR set. Shows network, broadcast, mask, wildcard, usable count — all in the browser.

Toggle any IPv6 address between its shorthand ::1 form and the fully-expanded 8-group representation, with reverse DNS and binary too.

Paste a raw email header to walk the Received hops in order, see the per-hop delay, and read off the SPF/DKIM/DMARC verdicts.

Build an HTTP Cache-Control header from a visual checklist — freshness, revalidation, immutability, and the common presets.

Build a CSP header from per-directive source lists, with three starter presets and live warnings for the dangerous wildcards.

Compose Access-Control-* response headers from a checklist, with four presets and live warnings for the dangerous combinations.