Instant radix and notation conversion across all /0 to /32 IPv4 subnet classes.
Execution runs 100% locally inside the browser sandbox using HTML5 Canvas, Web Cryptography Subtle API, and Web Workers. Zero egress.
Zero network latency. Operates completely offline with zero dependencies on third-party backend servers or cloud services.
Built according to official RFC specifications, cryptographic test vectors, and enterprise-grade data transformation standards.
Click any row in the /0 to /32 reference table or search for a specific mask.
View CIDR prefix, dotted decimal mask, Cisco wildcard mask, and total/usable host capacities.
Copy the complete subnet specification to configure network routers and firewalls.
The CIDR prefix represents the number of leading binary '1' bits in the 32-bit subnet mask (e.g. /24 has twenty-four 1s, resulting in 255.255.255.0).
Subtract each octet of the subnet mask from 255 (e.g., 255.255.255.255 - 255.255.255.0 = 0.0.0.255).
Zero-egress companion tools in the Security & Network suite
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Measure cryptographic randomness, Shannon entropy (0-8 bits/byte), Chi-square test, and byte distributions.
Generate secure RFC 6238 Base32 TOTP secret keys and standard otpauth:// URIs for Google Authenticator.
Construct and validate HTTP CSP headers and meta tags.
