42 free IT utilities

Expand a CIDR block into its network, broadcast, mask, and usable host range.

Split a network into equal subnets, or size subnets to a required host count.

Convert an IPv4 address between dotted decimal, integer, hex, binary, and IPv6 forms.

Query A, AAAA, MX, TXT, NS, CNAME, SOA, SRV, and CAA records for a domain.

Registration and ownership details for a domain or IP address.

Check whether a TCP port is reachable and accepting connections from the internet.

Measure reachability and latency, and trace the path to a host.

Convert a start and end address into the smallest set of CIDR blocks that covers it.

Generate a compliant RFC 4193 unique local address prefix.

Generate locally administered MAC addresses in any common notation.

Work out the real bandwidth a call consumes, including every layer of overhead.

Every SIP 1xx–6xx response, with what actually causes it in production.

Turn latency, jitter, and packet loss into an R-factor and MOS score.

Break a SIP message and its SDP body into headers, Via chain, and offered codecs.

Send a SIP OPTIONS ping over UDP, TCP, or TLS and read the response.

Generate strong random passwords or passphrases with configurable rules.

Estimate entropy and time-to-crack, and spot the patterns that weaken a password.

Compute MD5, SHA-1, SHA-256, SHA-384, and SHA-512 digests of text.

Verify a downloaded file against a published SHA-256 or MD5 checksum.

Decode a JSON Web Token's header and claims, and check its expiry.

Inspect a site's certificate: issuer, validity dates, SANs, and chain.

Compute an HMAC signature over a message with a shared secret.

Derive the current six-digit code from a TOTP secret, with the time window shown.

Build an HTTP Basic Authorization header, and the htpasswd command to match it.

Convert between octal, symbolic, and rwx Unix permissions, including the special bits.

Encode and decode Base64, including URL-safe variants.

Format, validate, minify, and convert between JSON and YAML.

Convert between binary, octal, decimal, hex, and any base from 2 to 36.

Reformat a SQL statement into readable, consistently indented form.

Test a regular expression against sample text with live match highlighting.

Compare two blocks of text and highlight what changed, line by line.

Write Markdown and see the rendered output side by side.

Count the tokens an LLM will actually bill for, and see where the text gets split.

Create a QR code for a URL, Wi-Fi network, contact card, or plain text.

Generate UUID v4 and v7 identifiers in bulk, plus ULIDs and nano IDs.

Random numbers, strings, hex, bytes, MAC addresses, and IP addresses.

Convert between Unix timestamps and human-readable dates across time zones.

Explain a cron expression in plain English and list its next run times.

Convert between HEX, RGB, HSL, and OKLCH, with contrast ratio checking.

Inspect response headers, redirect chains, and security header coverage.

Break a URL into its parts, decode the query string, and encode components.

Searchable reference for every HTTP status code and what it actually means.