HTTP status code reference with name, class, meaning, whether it is retryable or cacheable by default and related codes, or list a whole class
TCP and UDP port reference - the service on a port or the ports for a service name, port range type and an exposure risk rating for sensitive services
Parse a User-Agent string into browser, version, engine, OS, device type and architecture, and flag search, AI and social bots and HTTP tools
Decode a JWT header and claims without verifying it - issuer, subject, audience, issued, not-before and expiry times, lifetime and security warnings
Semantic version tools - compare two versions, check a version against an npm-style range such as ^1.2.0 or ~2.1, and compute the bumped next version
Infer a JSON Schema from a sample JSON document - types, nested objects and arrays, required fields and string formats like email, date, uri and uuid
Color palette from a hex color - complementary, split, analogous, triadic and tetradic harmonies, a 50 to 950 scale, tints, shades and WCAG contrast ratios
Modular typographic scale from a base size and ratio - px and rem for each step, line heights, CSS variables and fluid clamp() values between viewports
SaaS metrics from one month of MRR movements - net and gross retention, churn, ARPA, LTV, CAC, LTV to CAC, payback, quick ratio and Rule of 40
Split a hostname with the Public Suffix List into public suffix, registrable domain (eTLD+1) and subdomain, handling co.uk, com.au and github.io correctly
Marine species lookup in WoRMS - accepted name and status, authority, full classification, habitat flags, common names in many languages and other matches
Search the Catalogue of Life for accepted taxa - scientific name, authorship, rank, status, kingdom to genus classification and a link for each match
Drug and compound identifiers from MyChem - ChEMBL ID and max clinical phase, PubChem CID, formula, weight, IUPAC name, UNII and ChEBI ID
Convert a Gregorian date into the Islamic, Hebrew, Chinese, Persian, Indian, Buddhist, Japanese era, Coptic, Ethiopic and Minguo calendars with Julian day
Western and Orthodox Easter for any year from 1583 with Ash Wednesday, Palm Sunday, Good Friday, Ascension, Pentecost and Corpus Christi dates
Western zodiac sign with element, modality and ruling planet, Chinese zodiac animal and element, birthstone, generation and weekday for a birth date
ISO week number and label, day of year, days left, quarter for calendar and three fiscal years, leap year, Julian day and week start and end for a date
Count business days between two dates excluding weekends and optionally national public holidays for a country, with the next working day after the end
Black-Scholes-Merton price for European calls and puts with delta, gamma, vega, theta, rho, intrinsic and time value, moneyness and put-call parity check
Solve implied volatility from an observed option price using Black-Scholes, with delta, vega, a volatility regime label and the pricing error
Bond price from yield or yield to maturity from price with duration, modified duration, convexity, current yield and the price move for a one point yield change
Kelly criterion bet sizing from win probability and odds - full, half and quarter Kelly, expected log growth, break-even win rate and a verdict
Risk metrics from a price or return series - annualised return and volatility, Sharpe, Sortino, Calmar, max drawdown, 95 percent VaR, expected shortfall and skew
NPV, IRR, profitability index, payback and discounted payback for a cash-flow series with an accept or reject decision and NPV at several discount rates
