Developer toolbox

APCA Lc value for text over background, with the minimum size table.

Simulate protan, deutan, tritan and achromat vision, with luminance and contrast.

WCAG 2 contrast ratio for two colours, with AA and AAA verdicts.

Convert a color between HEX, RGB, HSL and HSV, with a preview swatch.

Mix colours with weights in RGB, linear RGB, HSL, Lab or OKLab.

Resolve named colours, or find the closest names for a value.

Build a 50 to 950 scale around a base colour, with OKLCH and Tailwind names.

Build linear, radial, conic or repeating gradients, plus an SVG preview.

Convert between OKLCH, OKLab, sRGB, HSL and hex, with a gamut check.

Pick a reproducible colour scheme, with contrast notes and OKLCH values.

Simplify a ratio, scale a size and find the nearest standard format.

Build a border radius from four corners and vertical radii, with CSS, SVG and Tailwind.

Compose box shadows and text shadows with colour, opacity and extra layers.

Convert between px, rem, em, pt and pc against a root font size.

Encode text to Base64, or decode Base64 back to plain text.

Decode BSON hex dumps into a readable tree and encode JSON back to BSON hex.

Preview the first rows of a CSV file with delimiter detection and row and column counts.

Turn CSV rows into a JSON array of objects, using the first row as the header.

Turn CSV rows into a GitHub-flavoured Markdown table with an optional header row.

Generate CREATE TABLE and INSERT statements from CSV rows with inferred column types.

Check a CSV file: delimiter, quoting, column count consistency and a preview.

Compare two texts and show the added, removed and unchanged lines.

Turn CREATE TABLE statements into a Mermaid or Graphviz entity-relationship diagram.

Beautify or minify GraphQL queries, mutations and fragments with brace validation.

Compress and decompress gzip, zlib and raw deflate payloads given as text or Base64.

Escape or unescape HTML entities in a string.

Strip HTML markup down to readable plain text while keeping block boundaries.

Validate JSON syntax with precise line and column errors, then beautify, minify or sort the keys.

Infer a draft 2020-12 JSON Schema from a sample JSON document.

Validate a JSON document against a JSON Schema and list every violation.

Flatten a JSON array of objects into CSV rows.

Convert a JSON document into XML, using the @attribute and #text conventions.

Convert a JSON document to YAML, or a YAML document back to JSON.

Validate tolerant JSON5 with comments, trailing commas, single quotes and unquoted keys.

Convert between JSON Lines and a JSON array in either direction.

Evaluate a JSONPath expression against a JSON document.

Drop duplicate lines while keeping the original order, optionally ignoring case.

Validate MongoDB-style queries and aggregation pipelines against known operators.

Convert an integer between base 2, 8, 10, 16 and 36, with arbitrary precision.

Pretty-print a SOAP envelope with consistent indentation while preserving CDATA.

Detect common SQL performance problems such as SELECT star and missing WHERE clauses.

Format or minify SQL with uppercase keywords, one clause per line and indented subqueries.

Convert a temperature between Celsius, Fahrenheit and Kelvin and show all three scales.

Convert between Unix timestamps and readable dates.

Convert a wall-clock time between two IANA time zones with offsets and DST state.

Convert a TOML document to JSON, keeping key order where the decoder allows.

Validate a TOML document and list its top-level keys with their value types.

Percent-encode text for use in a URL, or decode a percent-encoded string.

Pretty-print a WSDL document and list the operations it exposes.

Check that an XML document is well-formed (mismatched or unclosed tags) and re-indent it.

Convert an XML document into JSON, using the @attribute and #text conventions.

Convert a YAML mapping to TOML and refuse documents TOML cannot represent.

Validate YAML syntax, catch indentation errors and normalize the indentation.

Check whether a word or sentence reads the same forwards and backwards.

Convert text to binary digits and back, in bytes or nibbles.

Convert text to UPPER, lower, Title, Sentence, camelCase, snake_case, kebab-case and more.

Count characters, words or bigrams and rank them by frequency.

Replace literal text or a regular expression, with optional capture groups.

Convert HTML to Markdown: headings, lists, links, code blocks, quotes and tables.

Rank the significant words of a text with a TF-IDF score and a stop-word list.

Normalize Markdown: heading spacing, list markers, blank lines and hard breaks.

Check the structure and style of a Markdown document, with line numbers.

Render Markdown (GFM) to clean HTML.

Strip the Markdown syntax and keep the prose, the links and the tables.

Flesch, Flesch-Kincaid, Gunning fog, SMOG, ARI, Coleman-Liau and Dale-Chall.

Parse a regular expression and describe every node, group and flag.

Test a regular expression with flags, inspect matches and capture groups, and preview a replacement.

Rotate the Latin alphabet by any shift, with optional digits and case.

Escape or unescape JSON, XML, HTML, CSV, SQL and regex strings.

Validate, convert, shift, rescale and merge SRT and WebVTT files.

Trim, collapse or strip whitespace from every line, or expand tabs.

Sort lines alphabetically, by length, naturally or randomly, with deduplication.

Count words, characters, lines, sentences and paragraphs, with a reading time.

Inspect code points, UTF-8 bytes, UTF-16 units and normalisation forms.

Random postal addresses with street, city, region and postcode for the United States, the United Kingdom, Germany, France and Russia.

Generate Code 128 or EAN-13 barcodes as PNG.

Generate ISO 9362 BIC/SWIFT codes: a four-letter bank code, a two-letter country, a two-character location and an optional three-character branch.

Test card numbers for Visa, Mastercard, American Express, Discover, JCB and Diners Club with the correct IIN prefix, length and Luhn check digit.

Generate Bitcoin P2PKH, Ethereum and Tron addresses with the correct version byte, Base58Check encoding or EIP-55 checksum.

EAN-13, UPC-A and EAN-8 barcodes with a valid GS1 check digit, plus the check-digit computation shown step by step.

Build an HTML email signature in a classic, modern or minimal layout from a name, role, company and contact details.

Render a PNG favicon at 16, 32, 48, 64, 128 or 256 pixels from a background colour, a foreground colour, a letter or an emoji, and a shape.

Every registered HTTP status code with its RFC 9110 reason phrase, its category and a one-line meaning.

Generate ISO 13616 IBANs for 24 countries with the correct length, the national BBAN structure and valid MOD-97-10 check digits.

Check an IBAN: country length, character set, BBAN structure and the MOD-97-10 check, with the bank code and account number extracted where the layout is known.

Fifteen-digit IMEIs with a valid Luhn check digit and a TAC prefix, plus the sixteen-digit IMEISV variant with its software version.

ISO 6166 ISINs with a two-letter country, a nine-character NSIN and the check digit computed over the letter-expanded value.

Emit a complete open-source licence text — MIT, Apache-2.0, GPL, LGPL, AGPL, MPL, BSD, ISC, Unlicense, CC0, CC-BY or BSL — with the year and copyright holder filled in.

MAC-48 and EUI-64 addresses, including the locally-administered and multicast variants, with a selectable OUI prefix and separator.

Emit the meta block of a page together with its Open Graph and Twitter Card tags from a single form.

Generate compact URL-safe identifiers with a custom alphabet and length.

Build a web app manifest with name, start URL, scope, display mode, orientation, colours, icons, categories and screenshots.

Encode any text or URL into a PNG QR code.

Build a robots.txt with user-agent, allow, disallow, crawl-delay and sitemap rules.

Generate US ABA routing numbers with the weighted 3-7-1 checksum, or validate one you already have.

Emit a valid RSS 2.0 or Atom 1.0 feed from channel metadata and a list of items, with correctly formatted dates.

Build an XML sitemap from a list of URLs.

Build schema.org JSON-LD for Article, Product, Organization, Person, Event, BreadcrumbList, FAQPage or LocalBusiness ready to paste into a page.

Validate taxpayer identifiers of nine countries — US EIN and SSN, UK UTR, French SIREN and SIRET, German tax number and USt-IdNr, Spanish NIF and NIE, Italian codice fiscale and partita IVA, Canadian SIN, Australian ABN and Indian GSTIN — with the format, the checksum and the parsed parts.

Generate individual or company tax identification numbers with valid checksums for the United States, the United Kingdom, France, Germany, Spain, Italy, Canada, Australia and India.

Generate lexicographically sortable ULIDs (48-bit timestamp, 80-bit randomness).

Generate UUIDs: v4 random, v7 time ordered and v1 timestamp based.

Generate European VAT numbers for 28 countries with the national prefix, structure and check digits.

Check the format and checksum of a European VAT number offline. This is a format check only and never a VIES lookup.

Seventeen-character ISO 3779 vehicle identification numbers with the check digit in position nine and a decodable WMI, VDS and VIS split.

Encrypt or decrypt text with AES-256-GCM under a PBKDF2 passphrase.

Build or read the Authorization header for HTTP Basic authentication.

Hash a password with bcrypt, or check a password against an existing bcrypt hash.

Show the CRCs, the Adler-32 sum and the common digests of a piece of text.

Turn an origin, method and header list into the Access-Control response headers.

Read a CORS header block and flag the combinations browsers refuse.

Check a card number's Luhn digit and report its brand and expected length.

Assemble a Content-Security-Policy header from individual directives.

Read a PKCS#10 certificate request: subject, key, SANs and fingerprint.

Generate an ECDSA key pair on P-256, P-384 or P-521.

Generate an Ed25519 signing key pair in PKCS#8 and OpenSSH formats.

Validate an address against RFC 5322, check its IDN form and spot role mailboxes.

Remove the EXIF, XMP, IPTC and comment segments from a base64 JPEG.

Seal a file's contents into a downloadable AES-256-GCM blob, or open one again.

Compare two lists of hashes and show what they share and what only one side has.

Compute MD5, SHA-1, SHA-2, SHA-3 and BLAKE2 digests of any text.

Sign a message with a shared secret using HMAC-SHA-256, SHA-512, SHA-1 or MD5.

Decode and inspect a JSON Web Token: header, payload, registered claims and expiry.

Sign a JSON payload as an HS256, HS384 or HS512 JSON Web Token.

Verify a JSON Web Token's signature and report its claims and expiry.

Generate strong random passwords with a configurable length and alphabet.

Estimate the entropy, the character pool and the crack time of a password.

Read every certificate in a PEM bundle: subject, issuer, validity and fingerprints.

Generate a PKCS#8 RSA private key with its public key and OpenSSH form.

Compose an RFC 9116 security.txt document ready for the .well-known directory.

Scan Go code for string-built SQL and flag the patterns that invite injection.

Generate an Ed25519, ECDSA or RSA key pair and print the OpenSSH public key.

Encrypt and decrypt short text with AES-GCM, ChaCha20-Poly1305 or a plain XOR stream.

Draw cryptographically random tokens as hex, base64url, base58, UUID v4 or ULID.

Generate, parse and check time-based one-time passwords (RFC 6238).

Convert between bit and byte rates and work out the transfer time of a file.

Turn a curl command into Go, Python, JavaScript or PHP.

Resolve a hostname to its A and AAAA records.

Follow the Received chain hop by hop and check the authentication headers.

Build a header block from Name: value lines and check it against the chosen HTTP version.

Parse a raw header block into a table and flag duplicates and non-canonical names.

Expand or compress an IPv6 address and show its binary layout.

List the mail exchangers of a domain, lowest preference first.

Describe an IP address: family, scope, class, reverse name and reserved ranges.

List the authoritative name servers of a domain.

Search the well-known TCP and UDP ports by number, service or description.

Build a Postman v2.1 collection from a list of URLs.

Resolve an IP address back to its PTR name and show the containing block.

Inspect a remote certificate: validity dates, chain of trust, subject alternative names and days remaining.

Compute the network, mask and host range of an IPv4 or IPv6 CIDR block.

Fetch the TXT records of a domain and classify SPF, DKIM, DMARC and verification entries.

Split a URL into scheme, authority, path, query parameters and fragment.

Follow the redirects of a URL hop by hop and report each status, Location and timing.

Identify the browser, engine, operating system and device behind a User-Agent string.

Decode an RFC 6455 frame given as hex: opcode, mask, length and payload.

Query the registry of a domain or IP and extract the registrar, dates, status and name servers.

Decode a DER or BER structure from hex or base64 into a tree of tags, lengths and values.

Decompose a float into sign, exponent and mantissa, with neighbours, ULP and round-trip error.

Convert an octal or symbolic file mode into numeric, symbolic and special-bit forms.

Produce a unified diff between two texts with configurable context and an optional patch header.

Build a five-field cron expression from a preset or field by field, with the next runs.

Parse a five-field cron expression and show the next scheduled runs.

Indent and expand a CSS stylesheet.

Compress a CSS stylesheet by removing whitespace and redundant tokens.

Add or subtract a duration and measure the exact gap between two dates.

Build a docker-compose.yml from an image, ports, volumes, environment, healthcheck and dependencies.

Generate a multi-stage Dockerfile for Go, Node, Python, Rust or PHP.

Quote, escape and expand a .env block and render it as JSON, YAML or shell exports.

Assemble a Conventional Commits message and check the 50/72 column rules.

Build a workflow with a job matrix, steps, a cache key and an artifact upload.

Assemble a .gitignore from a stack selection plus your own patterns.

Indent an HTML document or fragment and tidy up tag nesting.

Compress HTML by removing whitespace, comments and redundant attributes.

Build a Huffman code, measure entropy and compression ratio and export the tree as Mermaid and DOT.

Build an HTML anchor, Markdown, reStructuredText, BBCode, mailto:, tel: and a plain-text entry from one URL.

Re-indent JavaScript while preserving strings, template literals, regexes and comments.

Compress JavaScript source with a real parser.

Generate TypeScript interfaces from a JSON Schema, resolving types, enums, items and $ref.

Generate Go structs with json tags from a JSON sample.

Generate TypeScript interfaces from a JSON sample, with unions and optional fields.

Minimise a truth table into a sum of products and a NAND-only form.

Generate a Deployment and Service, with an optional Ingress, from a handful of settings.

Generate placeholder paragraphs, sentences or words, with an optional HTML wrapper.

Identify a MIME type from a filename, a base64 blob or a text snippet, with charset and magic bytes.

Encode and decode ITU Morse with a selectable separator and an option to keep unknown characters.

Build an nginx server block with TLS, proxying, gzip, security headers and redirects.

Evaluate an expression with bitwise operator semantics and two's-complement wrapping for a chosen word size.

Derive a regular expression from example strings and check it against counter-examples.

Emit the equivalent regex snippet in eight languages and list the named groups and matches.

Parse an RSS 2.0 or Atom feed and check required elements, dates, GUID uniqueness and enclosures.

Compare two semantic versions, test a range expression and compute the next increment.

Intersect two or more semver ranges and return the resulting range or the empty set.

Turn any text into a URL-friendly slug.

Uppercase SQL keywords, break lines per clause and indent subqueries.

Work out the frame size, per-byte time, throughput, baud error and divisor latch for a UART frame.

Convert any unit across length, mass, area, volume, speed, temperature, data, pressure, energy and angle.

Project the future value of a deposit with recurring contributions and a compounding frequency.

Work out the monthly payment, the total cost and the interest of an amortising loan.

Work out the tip, the total bill and what each person owes.

Decode a three or four digit SMD resistor code into its resistance value.

Turn a list of course grades and credits into a weighted grade point average.

Convert cooking volumes and weights between cups, spoons, millilitres and grams.

Chart the physical, emotional and intellectual biorhythm cycles for a given day.

Estimate the basal metabolic rate and the daily energy expenditure from body metrics and activity level.

Estimate the due date and the trimester boundaries from the first day of the last period.

Find the bedtimes that let you wake up at the end of a full 90 minute sleep cycle.