NetPad — Subnet, CIDR & Timezone Tools

Subnet, CIDR, IP and timezone tools that run entirely on your machine.

Network and IT people need small answers constantly. What is the usable host range on this /27. Is this address inside that subnet. What time is it in Bangalore right now. What does this epoch timestamp mean. Today that means opening a new tab and pasting internal data into whichever ad-covered site ranks first. NetPad puts those answers in your toolbar instead, and does all the maths on your own machine. EVERYTHING RUNS LOCALLY NetPad makes no network requests of any kind. No server, no account, no analytics, no telemetry, no error reporting. Whatever you paste — internal ranges, hostnames, tokens, log timestamps — never leaves your computer. The manifest blocks outbound connections at the browser level, so this is enforced by Chrome rather than promised by us. Two permissions: contextMenus and storage. No host permissions, no page access, no content scripts. NetPad cannot read the pages you visit. SUBNET AND IP • Full breakdown: network address, broadcast, first and last usable host, host count, wildcard mask, prefix and netmask conversion • Point-to-point /31 links and single-host /32 handled correctly • "Is this address in this subnet?" both ways round • Private, public, reserved, multicast and documentation ranges identified • CIDR expansion, and the smallest set of blocks covering a range TIME • A timezone board of the cities you actually work with, live, as a split-flap departure board • Epoch conversion in both directions — seconds, milliseconds, microseconds and nanoseconds, with the unit worked out from the number • Meeting overlap: see the hours that work for everyone at a glance • Daylight saving handled properly, including the hour that does not exist when the clocks jump forward ENCODING • Base64 encode and decode, standard and URL-safe • JWT decode — header and payload, with the timestamp claims shown as real times and expiry flagged. The signature is not verified and NetPad says so; checking it would need the issuer's key and a network request. • URL encode and decode • JSON validate and pretty-print, with errors reported by line and column RIGHT-CLICK ANYTHING Highlight a line of a firewall log, right-click, and NetPad picks the addresses and the timestamp out of it and offers each one. It reads only the text you deliberately select — Chrome passes it directly to the extension, so no page access is needed. PASTE AND READ There is one field at the top. Paste anything into it and NetPad works out what it is. No choosing a tool first, no submit buttons, results as you type, every value one click to copy. FOR IT ADMINISTRATORS If your organisation manages extensions by permission, there is a page listing the extension ID, the complete permission list, the policy snippets for allowlisting, and how to verify the no-network claim yourself: https://net-pad.netlify.app/for-it-administrators.html Free, with no paid tier, no upsell and no account.