Network & web tools
Three tools for the plumbing of networks and the web: working out an IPv4 subnet, making text safe to put inside a URL, and turning a link, a Wi-Fi login or a contact card into a QR code.
All three compute their answers in the page. The addresses, URLs and Wi-Fi passwords you type are not sent anywhere — which matters, because URLs often carry session tokens and network plans describe infrastructure you would rather not publish.
All tools 3
Which tool for which job
- Find the network, broadcast and host range of a CIDR blockThe Subnet Calculator breaks down any IPv4 address in CIDR form: network address, usable host range, broadcast, subnet mask, wildcard mask, class and scope.
- Divide a network into smaller subnetsThe same subnet calculator splits a block into equal subnets at any longer prefix — a /16 into sixteen /20s, for instance — and lists each range.
- Put text safely into a query stringThe URL Encoder / Decoder percent-encodes a single value, including characters such as
&,=and/, exactly asencodeURIComponentwould. - See where a long redirect link really goesPaste it into the URL decoder to turn
%3A%2F%2Fback into readable text before you click. - Make a QR code for a link, a Wi-Fi network or a contactThe QR Code Maker covers web links, Wi-Fi, contact cards, phone numbers, text messages, e-mail, calendar events, locations and payment links, with an optional logo in the centre.
Limits worth knowing
- The subnet calculator is IPv4 only, and it takes the prefix as a number:
192.168.1.0/24, not a dotted mask. The results show the dotted mask for you. - Splits are into equal subnets. For a mixed plan, split the block, then paste one of the results back in and split that. Very large splits list the first 256 rows and tell you the true total.
- Cloud networks reserve extra addresses. AWS, for example, keeps five per subnet, so expect slightly fewer usable hosts in a VPC than the standard arithmetic shows.
- A plus sign is not decoded to a space. That rule belongs to HTML form encoding; standard percent-encoding writes a space as
%20. - Encoding twice is a classic bug. If a decoded result still contains
%25sequences, it was encoded twice — decode it again. - QR content is fixed once printed. The code holds the text itself, so it cannot be edited later. For a destination that may change, encode an address you control and redirect it at your end.
- A Wi-Fi code contains the password in readable form. Anyone who scans or photographs it can read it.
- Test before you print. A logo covers part of the pattern, and very long content — beyond roughly 1,200 characters — cannot be encoded at all.
How these tools work
The subnet calculator is 32-bit arithmetic: the network address is the IP combined with the mask, and the broadcast address is the network with the host bits switched on. The URL tool is a thin wrapper around the browser's own encoding functions, so its output always matches what your code would produce. QR codes are drawn by the open-source qrcode.js library at the highest error-correction level, which is what leaves room for a logo, and exported as a 256 × 256 pixel PNG.
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Frequently asked questions
Do the QR codes expire or track scans?
No. These are static codes: the link or text is encoded directly in the pattern, and scanning one goes straight to the destination without passing through this site. Nothing is counted or tracked, and the code keeps working for as long as the destination exists.
Does the subnet calculator support IPv6?
No, it is IPv4 only. IPv6 is planned differently — there is no broadcast address and subnets are conventionally /64 — so it needs a different tool.
What is the difference between encoding a component and encoding a whole URL?
Encoding a component escapes every character that has a meaning inside a URL, including slashes, question marks, ampersands and equals signs, so it is right for a single value such as one query parameter. Encoding a whole URL leaves those structural characters alone so the address keeps working, and escapes only spaces and non-ASCII characters.
Is it safe to type my Wi-Fi password into the QR code maker?
The code is generated in your browser and the password is not uploaded. Bear in mind that the finished code contains the password in readable form, so treat a printed Wi-Fi code like a written-down password.