DNS lookup
A, AAAA, CNAME, MX, NS, TXT and SOA in one go.
Handy during a migration: check whether the A, MX and TXT records have already propagated.
// sudo apt install handiness
Tools for developers and administrators
A set of tools I use myself every day, free and without an account. Read DNS, check certificates, review security headers, calculate subnets or generate a password that is actually strong. Everything runs here on the server or in your own browser, without anything being stored.
Check SSL certificate
Validity, remaining days and whether the chain is complete.
Watch the remaining days and a complete chain: a missing intermediate certificate often goes unnoticed in a browser, but does break integrations.
Whois lookup
Registrar, name servers and registration dates.
This shows which registrar holds a domain and when it expires. Handy before you request a transfer.
Security headers
Status code, redirects and the most important headers.
Six headers do most of the work: HSTS, CSP, X-Frame-Options, X-Content-Type-Options, Referrer-Policy and Permissions-Policy.
My IP address
Exactly what the rest of the internet sees of you.
IP location lookup
Country, city, time zone, provider and AS number of any address.
Works with an IP address and a domain name. Provider locations are an estimate: count on the city, not the street.
Subnet calculator
Network, range and number of addresses for IPv4 and IPv6.
Works with and without prefix. Leave the prefix out and I calculate with /32 for IPv4 and /128 for IPv6.
Colours and contrast
HEX, RGB and HSL side by side, with the WCAG check.
Text
Background
This is how the combination reads
And this is what smaller text looks like.
Password generator
Cryptographically random and never the same twice.
Passwords, colours and subnets are calculated entirely in your browser. DNS, certificates, whois, headers and IP locations go through my server, because a browser is not allowed to make those connections. We do not log those lookups.