Plan IPv4 allocations with split and join
Divide an IPv4 network into named allocations and join sibling blocks without losing sight of the address space.
Read guide →The field guide
A little context goes a long way.
One written guide per tool: what the input means, how to read the result, and the limits worth knowing before you act on it. Concrete examples, no filler.
Network & DNS
Read DNS answers, TTLs and negative responses
Inspect public DNS records with clear distinctions between answers, missing records and resolver failures.
Read guide →Understand what email DNS policy can tell you
Inspect published SPF, DMARC and a supplied DKIM selector, with the limits of DNS-only analysis made explicit.
Read guide →Investigate HTTP headers and redirect chains
Follow a bounded public redirect chain and examine status codes and response headers without loading the page.
Read guide →Trace a message through its email headers
Unfold message headers and inspect routing and reported authentication locally, without claiming to verify the sender.
Read guide →Security & identity
Translate Unix permissions without executing commands
Translate Unix permission bits, octal modes and symbolic changes, including setuid, setgid and sticky bits.
Read guide →Choose passwords and passphrases with useful entropy
Generate secrets with browser cryptographic randomness and clearly stated character or word selection rules.
Read guide →Read a JWT without mistaking decoding for verification
Read a three-part token and its timestamp claims locally; decoded content always remains unverified.
Read guide →Compare SHA checksums for text and files
Calculate SHA-256, SHA-384 and SHA-512 for text or bounded local files, with progress and cancellation.
Read guide →Development & data
Convert JSON and YAML without hiding data loss
Validate, format and convert structured text while protecting large numeric values from silent rounding.
Read guide →Work with URL components and duplicate query parameters
Inspect URL components and ordered query parameters or transform encoded text without visiting any address.
Read guide →Test JavaScript regex patterns with execution limits
Explore JavaScript regular expressions in a terminable worker with bounded input, match counts and execution time.
Read guide →Text & encoding
Use Base64 alphabets, padding and byte formats
Encode UTF-8 text or hexadecimal bytes and decode standard or URL-safe Base64 with explicit error reporting.
Read guide →Compare changes by line, word and whitespace
Compare text by line or word and export a unified difference without rendering input as HTML.
Read guide →Time & scheduling
Read five-field cron schedules across timezones
Inspect five-field cron schedules and upcoming instants in an explicit timezone using the documented parser rules.
Read guide →Convert epoch values with explicit units and offsets
Convert explicitly selected seconds or milliseconds to timestamp displays without guessing the unit or timezone.
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