Free tools
Network, Linux, Windows & email tools
Calculators, config generators and checkers I built for my own work. Free, fast and private – everything runs in your browser unless it needs a live DNS lookup.
IPv4 Subnet Calculator
Network, broadcast, usable host range, wildcard mask and binary view for any IPv4 address and CIDR prefix.
Open tool NetworkIPv6 Subnet Calculator
Prefix range, number of addresses and /64 networks, and a list of subnets when you split a delegation.
Open tool NetworkIPv6 Address Converter
Expand or compress any IPv6 address and see it as binary, decimal, hex groups and an ip6.arpa reverse DNS name – or turn a decimal number back into IPv6.
Open tool NetworkIPv6 Address Validator
Check whether an IPv6 address is valid and find out what kind it is – global unicast, link-local, unique local, multicast, documentation, IPv4-mapped and more.
Open tool NetworkIPv6 Cheat Sheet
IPv6 address types, special prefixes and prefix sizes on one page – a quick reference for planning and troubleshooting.
Open tool NetworkMAC Address Converter
Reformat a MAC address for Windows, Linux or Cisco, check its unicast/multicast and local/global bits, and derive the EUI-64 IPv6 link-local address.
Open tool NetworkIPv4 Address Converter
Convert an IPv4 address to decimal, hex, binary, octal and its IPv4-mapped IPv6 form – and back.
Open tool NetworkBandwidth & Transfer Time Calculator
How long will a backup, upload or migration take? Enter the size and link speed – with a realistic overhead allowance.
Open tool NetworkTCP/UDP Port Lookup
Search the well-known ports used by mail, web, remote access, databases, Windows domains and VoIP – with protocol and firewall notes.
Open tool Email & DNSDNS Lookup
Look up A, AAAA, MX, TXT, NS, CNAME, SOA, CAA, SRV and PTR records for any domain or IP address.
Open tool Email & DNSSPF, DKIM & DMARC Checker
Check a domain’s MX, SPF, DMARC and DKIM records in one go, with plain-English findings and fixes for common mistakes.
Open tool Email & DNSSPF Record Generator
Build a valid SPF TXT record for Microsoft 365, Google Workspace, your own mail server and sending services – with a lookup counter.
Open tool Email & DNSDMARC Record Generator
Create a DMARC policy record step by step – from monitoring (p=none) to full protection (p=reject) – with reporting addresses and alignment.
Open tool LinuxNetplan YAML Generator
Generate a correct Netplan file for a static IP or DHCP on Ubuntu 18.04 to 26.04 – with the right gateway syntax, file permissions and apply commands.
Open tool LinuxNginx Server Block Generator
Production-ready Nginx server blocks for WordPress/PHP-FPM, static sites and reverse proxies – HTTPS, HTTP/2, www redirect and security headers included.
Open tool Linuxsystemd Service Generator
Turn any script or app into a systemd service that starts on boot, restarts on failure and runs as a locked-down user.
Open tool LinuxCrontab Generator
Build a cron schedule from plain choices, read any cron expression in plain English and preview the next run times.
Open tool Linuxchmod Calculator
Tick read, write and execute for owner, group and others – or type an octal like 750 – and get the symbolic form and the command.
Open tool WindowsWindows Static IP Command Generator
Set a static IP, gateway and DNS on Windows 10/11 or Windows Server – as netsh or PowerShell commands, plus the commands to switch back to DHCP.
Open tool WindowsRobocopy Command Builder
Build a safe Robocopy command for migrations, mirrors and backups – multithreaded, with retries, logging and an optional dry run.
Open tool WindowsWindows Repair Command Generator
Pick the problem – corrupt system files, update failures, network trouble, disk errors – and get the right SFC, DISM, chkdsk or netsh sequence in the right order.
Open tool SecurityPassword & Passphrase Generator
Strong random passwords and memorable passphrases generated with your browser’s cryptographic random source – nothing is sent or stored.
Open tool SecurityHash & Checksum Generator
SHA-256, SHA-512 and SHA-1 for text or files – verify an ISO or installer against its published checksum without uploading it anywhere.
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