1234.nu

Compute a cryptographic hash (md5, sha1, sha256, sha512) of text.

Compute an HMAC of a message with a secret key.

Encode text to Base64, or decode Base64 back to text (UTF-8).

Percent-encode (encode) or decode a string for use in URLs.

Validate and pretty-print (or minify) JSON.

Convert YAML to pretty-printed JSON.

Convert JSON to YAML.

Generate one or more UUIDs: random v4 (default) or time-ordered v7 (RFC 9562).

Encode text to Morse code, or decode Morse (words separated by " / ") back to text.

Convert an integer (1–3999) to a Roman numeral, or a Roman numeral back to an integer.

Turn text into a URL-friendly slug (lowercase, hyphen-separated, accents stripped).

Convert an identifier between cases: camel, pascal, snake, kebab, constant, title.

Count characters, words, lines, and sentences in text.

Encode text to Base32 (RFC 4648), or decode Base32 back to text (UTF-8).

Encode text to hexadecimal, or decode hex back to text (UTF-8).

Encode special characters to HTML entities, or decode HTML entities back to text.

Apply a ROT13 or arbitrary Caesar shift cipher to text.

Compute the CRC32 checksum of text.

Convert an integer between number bases (2–36).

Compress text (gzip, deflate, brotli, or zstd) and return Base64, or decode Base64 back to text.

Decode a JWT (JSON Web Token) into its header and payload.

Generate a cryptographically random password.

Parse a CSS color (hex like #3af or #33aaff, or "rgb(r,g,b)") and return hex, rgb, hsl, oklch, oklab, lab (CSS Color 4 D50) and naive CMYK forms.

Generate lorem-ipsum placeholder text by words, sentences, or paragraphs.

Set operations on two newline-separated lists: union, intersection, items only in A, or only in B.

Validate an IBAN, credit-card number (Luhn), BIC/SWIFT code, ISBN-10/13, or EU VAT number.

Convert a JSON array of objects into a GitHub-flavored Markdown table (union of keys as columns).

Evaluate a math expression (e.g.

Turn words into numeronyms — internationalization → i18n, accessibility → a11y.

Canonicalize email addresses — lowercase, strip Gmail dots and +tags — and dedupe.

Convert a JSON object to XML.

Escape or unescape a string for a target format: JSON string body, regular-expression literal, HTML entities, SQL LIKE wildcards, POSIX shell single-quoting, or URI component.

Sort, reverse, deduplicate, shuffle, or count line frequency in newline-separated text.

Flip text upside-down (Unicode substitution + reversal), mirror it (reverse only), or both.

Convert text to leetspeak.

Run a chain of operations (a "recipe") over an input, like CyberChef / the /forge web tool.

Ohm's law solver.

Decode resistor color bands into a resistance value.

Series resistor for an LED or series string.

Two-resistor voltage divider.

Cutoff/resonant frequency of a passive filter.

555 timer calculator.

Reactance of a capacitor or inductor at a frequency.

American Wire Gauge properties for a gauge number (awg, -3 = 0000 to 40).

Convert between a ratio and decibels.

Closed-loop gain of an op-amp from its resistors.

LM317 regulator output.

Voltage drop down a cable run (DC / 1-phase / 3-phase) from length, current and cross-section.

Minimum PCB copper trace width for a current using IPC-2221.

Series/parallel battery pack totals — pack voltage, capacity, energy and cell count from a cell spec.

Series resistor for a zener shunt regulator.

DC operating point of a voltage-divider biased BJT.

Smoothing capacitor for a rectifier from load current and target ripple.

Recommended fuse rating from load current (and optional inrush).

PWM duty cycle to average/RMS voltage and timing (or supply→duty for a target average).

Convert NTC thermistor resistance ↔ temperature using the Beta model (r0/beta) or Steinhart-Hart (a/b/c).

Convert between frequency and wavelength (λ = velocity_factor · c / f).

Physical antenna lengths (full/half/quarter/⅝-wave) from a frequency, scaled by a velocity factor for real wire.

Free-space path loss in dB from distance and frequency: 20·log10(d_km) + 20·log10(f_MHz) + 32.44.

Received power and link margin: Prx = Ptx + Gtx + Grx − path_loss − other_loss; margin = Prx − sensitivity.

LoRa time-on-air (Semtech formula) from payload, SF, bandwidth and coding rate.

Decode a Modbus data address (5-/6-digit Modicon convention) to its register table, function code, access and zero-based PDU offset.

Time-on-air (ms) for a Meshtastic packet given a modem preset and data payload size (the 16-byte header and 16-symbol preamble are included).

Build a shareable Meshtastic channel URL (meshtastic.org/e/#…) from a name, modem preset and region.

Decode a Meshtastic channel URL (meshtastic.org/e/#…) back to its name, modem preset, region and key type.

Estimate annual rooftop solar yield (kWh/year) from array size, regional specific yield, orientation and tilt factors.

Home-battery payback: annual saving and payback years from capacity, price, efficiency, daily cycles and buy vs feed-in prices.

EV charging time between two states of charge, modelling DC rapid-charge taper above 80%.

Yearly energy and CO₂ for one device from power, daily run-time and grid carbon intensity (g/kWh).

Compare two semantic versions.

Does a version satisfy a range?

Compute the next version for a bump type: major, minor, patch, premajor, preminor, prepatch, prerelease.

Lint a Dockerfile against Hadolint-style best-practice rules.

Structurally validate an OpenAPI 3.x / Swagger 2.0 document (JSON or YAML).

Dew point (°C) from air temperature (°C) and relative humidity (%), via the Magnus formula.

Apparent ("feels-like") temperature in °C — wind chill when cold, heat index when hot — from temp (°C), wind (km/h) and humidity (%).

Moon phase for a date (ISO 8601, or now if omitted): name, illuminated fraction and age in days.

Sun azimuth (° from north) and altitude (° above horizon) for a date/time and location.

Great-circle distance (km) and initial bearing (°) between two lat/lon points, via Haversine.

Convert decimal-degree lat/lon to DMS strings and an MGRS grid reference.

Magnetic declination (° east-positive, true = magnetic + declination) from the World Magnetic Model 2025, for a lat/lon, optional elevation (m) and date.

Calories burned: MET × body-weight(kg) × hours.

Naismith's-rule hiking time (hours) from distance (km) and ascent (m), with adjustable flat pace and climb rate.

Scramble the inner letters of each word (4+ letters), keeping the first and last in place — the text stays readable.

Add Unicode combining marks to text for a glitch / zalgo effect.

Generate realistic but fake test data — names, emails, addresses, Luhn-valid cards, IBANs, plus Dutch KVK / BSN / BTW numbers, a full persona, or a full company profile.

Generate fake test data from a custom schema you define: a list of named fields, each with a type (name, email, uuid, bsn, iban, city, …).

Format a number as words, hex, binary, octal, scientific notation and a grouped decimal.

Convert a value between units of length, mass, data, speed, area, volume or temperature.

Everyday percentage math.

Primality test and integer factorization, with the next and previous primes.

Descriptive statistics for a list of numbers (space/comma/newline separated): count, sum, min, max, range, mean, median, mode, sample & population variance/stddev, and percentiles.

Evaluate an exact fraction/arithmetic expression (e.g.

Greatest common divisor and least common multiple of a list of integers, with Bézout coefficients for two numbers.

Factorial, permutations (nPr), combinations (nCr), permutations/combinations with repetition, and derangements (!n) for integers 0 ≤ r, n ≤ 5000.

Solve a polynomial from its coefficients (highest power first): [a,b] linear, [a,b,c] quadratic, [a,b,c,d] cubic.

Matrix operations: add, subtract, multiply (a and b); transpose, determinant, inverse, rank, trace (a only).

Finance math.

Bitwise calculator over a fixed width (8/16/32/64): and, or, xor (a,b); not, shl, shr (logical), sar (arithmetic) (a, with b as shift).

Decompose a number into its IEEE-754 form (sign, exponent, mantissa, hex bytes, class).

Convert text to space-separated 8-bit binary (UTF-8 bytes), or decode binary back to text.

Break text into its Unicode code points: character, U+ value, decimal, HTML entity and UTF-8 bytes.

Classic hex dump of text (UTF-8): 16 bytes per row with offset, hex columns and an ASCII gutter.

String utilities: trim, trim_lines, upper, lower, pad_left, pad_right, truncate, wrap, repeat, number_lines, remove_blank, remove_dupes, reverse, reverse_lines, count.

Reveal invisible characters in text — tabs, non-breaking spaces, zero-width characters, BOM and carriage returns — as glyphs, with a count of each.

Turn CSV/TSV (or pipe/semicolon-delimited) data into an aligned GitHub-flavored Markdown table.

Parse a URL or query string into its parameters (URL-decoded; repeated keys preserved).

Parse a .env file into a JSON object (action "parse"), or render a JSON object back into .env lines (action "generate").

Convert CSV to a JSON array of objects (direction "csv2json"; first row is headers) or a JSON array back to CSV ("json2csv").

IPv4 subnet calculator.

Carve an IPv4 network into variable-length subnets that fit a list of host requirements (largest first).

Parse a User-Agent string into browser, engine, OS and device type.

Hash a password with scrypt (action "hash"), or verify a password against a stored scrypt hash (action "verify").

Generate a TOTP (RFC 6238) one-time code from a Base32 secret.

Spell text using the NATO phonetic alphabet (Alfa, Bravo, …).

Convert text to alternating-caps "mocking SpongeBob" style.

Restyle text with Unicode look-alikes: bold, italic, bold_italic, script, fraktur, double_struck, monospace, fullwidth, circled, squared, small_caps, strikethrough, underline.

Roll dice in NdM±K notation (e.g.

Blue hour, golden hours and twilight for a location and date.

Sunrise, sunset, solar noon, civil twilight and day length for a location and date.

Build an HTTP Basic "Authorization" header and an Apache .htpasswd {SHA} line for a user/password.

Pretty-print / format a SQL query.

Lint a commit message against Conventional Commits — type, scope, breaking change, header length — and the semver bump it implies.

Generate a BIP39 mnemonic from fresh or supplied entropy (action "generate"), or validate a mnemonic and recover its entropy (action "validate").

Compose a .gitignore from per-stack templates.

Unwrap redirect-wrapped links (Outlook SafeLinks, Google, Facebook, YouTube, Proofpoint urldefense) and strip common tracking parameters (utm_*, fbclid, gclid, ...).

Convert an inclusive IPv4 address range (start to end) into the minimal set of CIDR blocks that covers it exactly.

Count business days between two dates (inclusive), skipping weekends and an optional list of holidays.

Decode CBOR bytes (hex or base64, auto-detected) into JSON.

Lint (usually untrusted) text for prompt-injection patterns: instruction-override phrases, invisible/zero-width unicode, Unicode Tags-block smuggling, bidi (Trojan-Source) controls, and markdown/HTML image exfiltration.

Validate an llms.txt file against the llmstxt.org format (required H1 title, optional blockquote summary, H2 link sections).

Grade an AGENTS.md / CLAUDE.md for completeness against the sections coding agents rely on (overview, setup, build/run, testing, conventions, structure, git/PR, gotchas).

Decode raw Protocol Buffers bytes (hex or base64, auto-detected) without the .proto schema — like `protoc --decode_raw`.

Compare two texts and return the differences.

Deep structural diff of two JSON documents (ported from /jsondiff): key order is ignored, arrays are compared by index.

Validate a JSON document against a JSON Schema (ported from /jsonschema: the same draft-07 / 2020-12 keyword subset — type, enum, const, properties/required/additionalProperties, items/prefixItems, allOf/anyOf/oneOf/not, local $ref, numeric/string/array/object bounds), or infer a draft-07 JSON Schema from a sample JSON document.

Infer TypeScript types from a JSON document (ported from /types): objects become exported interfaces, arrays merge shapes across elements (producing unions and optional fields for mixed shapes), and repeated names get suffixed.

Solve a triangle from any 3 known measurements (sides a/b/c and/or angles A/B/C in degrees, at least one side).