Site A Utilities

Utilities and guides for formatting, validating, and shipping developer data.

Calculate an exact age in years, months, and days for any reference date.

Encode UTF-8 text to Base64 or decode Base64 back to UTF-8 text.

Validate a five-field cron expression, describe it, and list its next run times.

Compute the number of days between two dates or add a number of days to a date.

Format and validate JSON while preserving large integers.

Check whether a document is valid JSON and report the first syntax error with its position.

Calculate a percentage of a number, what percent one number is of another, or percent change.

Test a regular expression against a subject and inspect matches and capture groups.

Count characters, words, lines, sentences, and paragraphs, and estimate reading time.

Convert between Unix timestamps in seconds or milliseconds and ISO-8601 instants.

Convert a value between length, mass, temperature, data-size, and time units.

Percent-encode or decode URL text, for whole URLs or single components.

Generate RFC 9562 version 4 (random) or version 7 (time-ordered) UUIDs.

How to format and validate JSON without losing precision, comments, or trust.

A step-by-step guide to proving that a page renders its content without client JavaScript.

A plain-language reference for the JSON data interchange format, its grammar, and its limits.

When to reformat JSON and when to validate it, and why the two tools answer different questions.