NSToolKit
Free online network, DNS, security, and developer tools. No signup required.
DNS Lookup
Query A, AAAA, MX, TXT, CNAME, NS, SOA records for any domain
MX Record Lookup
Find mail exchange servers and their priority for any domain
Reverse DNS Lookup
Find the hostname associated with any IP address (PTR record)
DNSSEC Checker
Verify DNSSEC signatures and chain of trust for any domain
SPF Record Checker
Validate SPF records and check email sending authorization
DMARC Lookup
Check DMARC policy: none, quarantine, or reject
DKIM Lookup
Verify DKIM public key records by domain and selector
Email Header Analyzer
Paste raw email headers to trace delivery path and detect spoofing
IP Blacklist / RBL Check
Check if an IP or domain is listed on 50+ spam blacklists
Email Deliverability Test
Send a test email to a generated address and get a full SPF/DKIM/DMARC/PTR/RBL report
What Is My IP
Instantly see your public IP address and basic network info
IP Geolocation Lookup
Find the country, city, ISP, and ASN for any IP address
WHOIS Lookup
Get domain registration details, owner info, and expiry dates
Ping Test
Ping any host from the server and measure round-trip latency
Traceroute
Trace the network path from the server to any host
ASN Lookup
Find the Autonomous System Number and owner for any IP
SSL Certificate Checker
Validate TLS/SSL certificates, expiry dates, and chain of trust
HTTP Security Headers
Inspect and grade HTTP response headers for security best practices
Password Generator
Generate cryptographically secure random passwords
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from text
JWT Decoder
Decode and inspect JSON Web Tokens without verifying signature
Subnet Calculator
Calculate network address, broadcast, host range, and mask for any CIDR
CIDR to IP Range
Convert a CIDR block to its full first/last IP address range
Port Reference Lookup
Look up any TCP/UDP port number to see the associated service
Bandwidth Calculator
Calculate transfer time or required bandwidth for any file size
IPv4 ↔ IPv6 Converter
Convert IPv4 addresses to IPv4-mapped IPv6 format and back
Base64 Encoder / Decoder
Encode text or decode Base64 strings instantly in your browser
URL Encoder / Decoder
Percent-encode URLs or decode encoded strings
JSON Formatter & Validator
Format, validate, and pretty-print JSON with syntax highlighting
Cron Expression Builder
Build and explain cron schedules with a visual interface
Unix Timestamp Converter
Convert Unix timestamps to readable dates and vice versa
Website Technology Inspector
Detect the web server, CMS, CDN, hosting provider, and tech stack behind any URL
UUID Generator
Generate cryptographically random UUID v4 and v7 identifiers
Regex Tester
Test regular expressions against input with live match highlighting
HTML Entity Encoder / Decoder
Encode special characters to HTML entities or decode them back
Text Diff Tool
Compare two text blocks and highlight line-by-line differences
YAML ↔ JSON Converter
Convert between YAML and JSON formats instantly
Number Base Converter
Convert numbers between binary, octal, decimal, and hexadecimal
IP Bogon / Private Range Checker
Classify any IP address as public, private, loopback, CGNAT, or reserved
IPv6 Subnet Calculator
Calculate network address, host range, and prefix info for any IPv6 CIDR
DNS Propagation Checker
Check if a DNS record has propagated across 10+ global resolvers
CAA Record Lookup
Check which Certificate Authorities are authorized to issue SSL certs for a domain
Open Port Checker
Test if a specific TCP port is open or closed on any host
HTTP Status Checker
Fetch any URL and see the HTTP status code and redirect chain
SMTP Connection Test
Test SMTP port connectivity and read the banner from any mail server
MAC Address / OUI Vendor Lookup
Identify the hardware vendor of any MAC address using the IEEE OUI registry
BIMI Record Checker
Validate BIMI DNS records and logo URLs for brand indicators in the inbox
MTA-STS Checker
Verify MTA-STS DNS record and fetch the policy file to confirm SMTP TLS enforcement
TLS-RPT Checker
Look up SMTP TLS reporting records and see where TLS failure reports are sent
ARC Chain Analyzer
Parse Authenticated Received Chain headers from a raw email to trace how forwarding handled authentication
SMTP Bounce Code Lookup
Search SMTP reply codes and enhanced status codes to decode bounce messages
CORS Headers Checker
Send a CORS preflight to any URL and inspect Access-Control headers