Know what your network is doing.
Check IPs, domains and MAC addresses, plan subnets, and troubleshoot the networks and software you manage.
Free tools with no account or AI processing. Calculations stay in your browser; external lookups run only after a clear provider disclosure and your action.
Quick checks. Clear next steps.
Small utilities for network operators, developers and people troubleshooting their own systems.
Start with a quick check
IPv4 Subnet Calculator
Calculate IPv4 network, broadcast, address range, wildcard mask and usable host count from a CIDR block.
Open toolIPv6 Subnet Calculator
Calculate the network prefix, address range and total address count for an IPv6 CIDR block, entirely in your browser.
Open toolIP Range to CIDR Converter
Convert an IPv4 start and end address into the smallest set of CIDR blocks that covers the range.
Open toolMAC Address Vendor Identifier
Identify a MAC address vendor automatically from a locally stored IEEE assignment registry.
Open toolIP Location & ISP Lookup
Find approximate location and ISP details for a public WAN address, with RDAP registration information when the location provider is unavailable.
Open toolDomain to IP & Reverse DNS
Check DNS A, AAAA and PTR records with a clear resolver disclosure before a lookup.
Open toolMy Public IP
Check the public IP address seen by an external service, only when you choose to run the check.
Open toolClear about data
Calculations stay in your browser. External lookups send data only after a clear provider notice and your action.
Built for real tasks
Get an answer, understand its limits, and follow a practical troubleshooting guide.
Lightweight by design
No account, app install or AI service is needed for these tools.
Everyday file tools
Percentage Change Calculator
Calculate the percentage increase or decrease between an original value and a new value, with the amount changed and the formula shown.
Open toolCSV Cleaner
Trim unwanted whitespace and remove empty rows from CSV data, with a change report before download.
Open toolExcel & CSV Compare
Compare two spreadsheets by a unique identifier and download a report of added, removed and changed records.
Open toolCSV & Excel Converter
Convert CSV data to an Excel worksheet or export one Excel worksheet as CSV while keeping identifiers as text.
Open toolMerge Spreadsheets
Combine Excel or CSV tables into one file by matching column headings, even when the column order differs.
Open toolSplit Spreadsheet
Split one CSV or Excel worksheet into smaller CSV files, repeating the header in every file.
Open toolSpreadsheet Duplicate Finder
Find repeated spreadsheet records using selected columns, then download unique rows and duplicate rows separately.
Open toolPractical technology guides
How to summarize an IP range into CIDR blocks
Represent an IPv4 start and end address as the smallest set of exact CIDR blocks.
Read guideIPv6 prefixes and subnet ranges explained
Understand IPv6 CIDR prefixes, compressed notation, address ranges and why IPv6 has no broadcast address.
Read guideMAC address formats and randomized addresses
Read a MAC address format and understand its unicast, multicast and local-administration bits.
Read guide