Developer Tools 99 tools

Pretty-print, validate, and minify JSON. Errors are surfaced inline. Nothing leaves your browser.

Shortcut: jfjs

Test regular expressions live. Highlights matches, lists capture groups, toggles flags, and ships a preset library (email, URL, IPv4, UUID, hex colour).

Shortcut: rtre

Compute SHA-1, SHA-256, SHA-384, or SHA-512 hashes of text using Web Crypto. Live, hex or base64url output, no upload.

Shortcut: hgha

Encode or decode URL strings. Component mode, URI mode, and encode-all mode (encodes tilde too). UTF-8 aware, live, no upload.

Shortcut: uedu

Paste a CSS selector and see its specificity as the (a, b, c) tuple. Handles :is(), :not(), :has(), :where(), :nth-child(… of …), attribute selectors, pseudo-elements, and comma lists. Compare two selectors side-by-side. Pure client-side, no upload.

Shortcut: cscs

Minify CSS for production (strip comments, shorten colors, zero lengths) or pretty-print it for reading. Live byte savings.

Shortcut: cmfc

Paste a cron expression and see what it means in plain English, plus the next 10 runs in your local time. Live, no upload.

Shortcut: ceec

Parse, lint, and format robots.txt files. Catches full-site block, bad Sitemap URL, missing colons, stacked groups. Live, in-browser, no upload.

Shortcut: rvlr

Preview how your page will look in Google, X, Facebook, LinkedIn, and Slack. Length checks, copy-ready meta tags. Live, in-browser, no upload.

Shortcut: mtsp

24 common regex tokens, click-to-load playground, live match highlighting with capture groups and named groups. In-browser, no upload.

Shortcut: rcre

Compare two JSON documents and see what changed, was added, or was removed at every path. Side-by-side tree, inline tree, or copy as JSON Patch. Live, in-browser, no upload.

Shortcut: jdjs

Validate an IBAN in your browser. Strips spaces and dashes, looks up the country, checks length and BBAN shape, runs the ISO 7064 mod-97 check-digit test. Single input or one-per-line bulk, copy results as TSV. 65 countries in the registry. Live, in-browser, no upload.

Shortcut: ivib

Paste a JSON Web Token and see its header, payload, and signature, with time-based claims (iat, nbf, exp) shown as UTC and relative time. Signature is displayed but not verified — we don't have your key. Live, in your browser, no upload.

Shortcut: jdjw

Type a tiny Mermaid-style DSL (participants, messages, notes) and see a hand-rolled SVG sequence diagram. Solid / dashed arrows, self-loops, left / right / over notes. Copy or download the SVG. Pure client-side, no upload.

Shortcut: sdrs

Type a value at a small and a large viewport, get a ready-to-paste CSS clamp() expression that scales fluidly in between. Breakpoint and font-size presets, live preview at any width, copy with one click. Pure client-side math, no upload.

Shortcut: cccs

Convert an integer between binary, octal, decimal, and hexadecimal in your browser. Arbitrary precision via BigInt, optional two's-complement for signed values (8 / 16 / 32 / 64 bits), bulk mode with copy-as-TSV. Pure client-side, no upload.

Shortcut: nbcn

Look up any HTTP status code. Paste a code (404) or a reason phrase (404 Not Found, too many requests), browse the catalogue by class (1xx–5xx) and kind (standard, WebDAV, Cloudflare, nginx, …), copy a reason line or an HTTP/1.1 status line. Pure client-side, works offline.

Shortcut: hscl

Paste a URL and see its scheme, host (with subdomain/domain/TLD split and IPv4/IPv6/IDN detection), port, path segments, query parameters, and fragment. Tweak any field and the rebuilt URL updates live. Pure client-side, no upload.

Shortcut: upur

Convert a date and time between any two IANA time zones. See the offset, DST flag, and a meeting-time strip across every zone you add. Pure client-side, works offline once loaded, no upload.

Shortcut: tzct

Build a Unix file mode (chmod) by clicking read / write / execute for owner, group, and other. See the 3- or 4-digit octal and the 10-character symbolic form (like `ls -la`). Toggle setuid, setgid, and sticky bits. Paste a mode and the grid follows. Pure client-side, no upload.

Shortcut: cchm

Encode text as HTML entity references (&name;, &, &) or decode entity-encoded strings back into characters. Five encoder modes, optional whitespace preservation, handles & without trailing semicolon. Pure client-side, works offline, no upload.

Shortcut: heed

IPv4 subnet calculator in your browser. Type an IP and CIDR prefix, see the network address, broadcast, netmask, wildcard, host counts (with RFC 3021 /31 handling), IP class, and flags for private / loopback / link-local / multicast ranges. Bulk parser, 12 common-prefix presets. Pure client-side, no upload.

Shortcut: scsu

IPv6 subnet calculator in your browser. Type an address and a /0..128 prefix, see the network, netmask, wildcard, total address count, first and last in range, and flags for private (RFC 4193), link-local, loopback, multicast, documentation (RFC 3849), and IPv4-mapped (::ffff:0:0/96) ranges. BigInt math for the full 128-bit range. Bulk parser, 8 common-prefix presets. Pure client-side, no upload.

Shortcut: iscs

Compose a .gitignore in your browser from curated templates — 10 languages (Node, Python, Rust, Go, Java, Ruby, PHP, .NET, Elixir, Swift), 9 frameworks (Next.js, Nuxt, React, Vue, Django, Rails, Laravel, Flutter, Astro), 5 editors (VS Code, IntelliJ, Vim, Emacs, Sublime), and 3 OSes (macOS, Windows, Linux). Live preview with pattern de-duplication, linter for trailing whitespace / anchored paths / negations, copy or download. Pure client-side, no upload.

Shortcut: ggit

Visual builder for CSS grid-template-columns and grid-template-rows. Set per-track values (fr, px, %, auto, minmax, fit-content), column and row gaps, justify/align-items, and grid-auto-flow. Live preview with numbered cells, per-track validation, copy-ready CSS, and five built-in presets (3-col, 12-col, sidebar, holy grail, auto-fit cards). Pure client-side, no upload.

Shortcut: cggc

Visual builder for CSS flexbox. Set container properties (flex-direction, flex-wrap, justify-content, align-items, align-content, gap) and per-item properties (flex-grow, flex-shrink, flex-basis, order, align-self). Live preview with 1–24 numbered items, copy-ready CSS with customisable selector, four built-in presets (row of cards, centered column, nav bar, stacked form). Pure client-side, no upload.

Shortcut: cfgc

Build a CSS cubic-bezier() easing curve visually. Drag the two control points on the graph, pick a preset (linear, ease, ease-in, ease-out, ease-in-out, step-start, step-end, plus easeInBack / easeOutBack / easeInOutBack), paste any CSS easing string, see a live animated preview, and copy ready-to-paste CSS for transition-timing-function and animation-timing-function. Pure client-side, works offline, no upload.

Shortcut: cecb

Generate a valid sitemap.xml from a list of URLs in your browser. Per-row lastmod, changefreq, and priority (separated by TAB, two-or-more spaces, or a vertical pipe). Lints bad URLs, out-of-range priorities, unknown changefreq values, and duplicate <loc>s. Copy or download the XML. Pure client-side, no upload.

Shortcut: sgsi

Pretty-print or minify an SQL statement in your browser. SELECT, FROM, WHERE, GROUP BY, ORDER BY, JOIN, WITH (CTE), INSERT, UPDATE, DELETE handled. Keyword case, indent, and semicolons configurable. Pure client-side, no upload.

Shortcut: sfms

Paste HTML on the left and a CSS selector on the right — matched elements highlight in the live preview frame. Per-match tag, id, classes, text preview, and a short selector path. Standard CSS selector syntax with comma lists, attribute, and pseudo-class support. Pure client-side, sandboxed preview, no upload.

Shortcut: cstc

Build a CSS triangle in your browser. Four directions, isosceles (border-trick) or equilateral (60° apex via clip-path), any colour, live preview, and copy-ready CSS class or inline style. Pure client-side, no upload.

Shortcut: ctag

Paste any CSS @media query and see when it matches. Plain-English breakdown, viewport simulator with width / height / DPR / color-scheme / hover / pointer / reduced-motion, and a 10-device matrix from Galaxy Fold to QHD. Supports classic `(min-width: 768px)` and modern range `(width <= 1024px)` syntax. Pure client-side, no upload.

Shortcut: cmqt

Convert any CSS value into every other unit. px, rem, em, %, vw, vh, pt, pc, in, cm, mm, q, ex, ch, sv*/lv*/dv*/cq*. Editable root font size, viewport, and container size. Bulk mode (one per line). Pure client-side, no upload.

Shortcut: cucs

Paste any User-Agent string and see it broken down into browser family + version, OS family + version, device vendor / model, and an overall device type (desktop, mobile, tablet, tv, console, bot). Detects 28 common crawlers (Googlebot, Bingbot, GPTBot, ClaudeBot, curl, wget). Five working presets included. Pure client-side, no upload.

Shortcut: uapu

Validate any credit, debit, or gift card number against the Luhn (mod-10) checksum in your browser. Detects Visa, Mastercard, Amex, Discover, JCB, Diners, Maestro, UnionPay, Mir, Verve from the leading IIN. Includes 6 test-card presets, length-vs-brand mismatch warnings, bulk-mode TSV export, and a 5-second idle mask that hides the PAN from shoulder-surfers. Pure client-side, never uploaded.

Shortcut: cclv

Paste a JSON sample and get a TypeScript interface (or type alias) inferred from its shape. Nested objects become named helper types; mixed-type arrays collapse into unions. Pure client-side, no upload.

Shortcut: jttj

Paste a Markdown document and get a list of findings — heading hierarchy skips, mixed list markers, code-fence issues, broken links and references, missing image alts, trailing whitespace, empty headings, and more. Configurable rules, copy findings as TSV or Markdown. Live, in your browser, no upload.

Shortcut: mlmd

Minify SVG by stripping comments and the XML declaration, dropping unused namespace declarations, collapsing whitespace, shortening numbers and hex colors, and removing empty attributes. Live byte count, side-by-side preview, and pretty-print mode. Pure client-side, no upload.

Shortcut: soms

Paste a CSV, TSV, or pipe-delimited file (or one number per line) and see per-column summary statistics — count, mean, median, mode, harmonic / geometric mean, variance, stddev, Q1/Q3, IQR, outlier count, skewness, kurtosis — plus a histogram. Optional log10 / sqrt / z-score transform, outlier drop, manual or auto (Sturges) bin count, and a copy-ready TSV. Pure client-side, no upload.

Shortcut: cvcs

Parse SemVer 2.0.0 versions, compare two with the full operator set, and match them against npm-style ranges — caret (^1.2.3), tilde (~1.2.3), hyphen (1.2.3 - 2.0.0), x-ranges, OR, exact, and the six comparators. Bulk max-satisfying finder and seven bump modes. Pure client-side, no upload.

Shortcut: scrc

Mint a JSON Web Token in your browser. Pick HS256, HS384, or HS512; type a header and a payload as JSON; supply a shared secret; the tool computes the HMAC signature with SubtleCrypto and shows the signed token. Mismatched-alg and weak-secret guardrails, byte and entropy counters, one-click random secret, signed-token breakdown, and a claims table with iat / nbf / exp shown as UTC and relative time. Pure client-side, the secret never leaves your browser.

Shortcut: jsjw

Compose an HTTP request with a form (method, URL, headers, body, basic auth, query params) and copy it as a cURL command, a fetch() call, a Python requests snippet, a Go net/http snippet, or a Node https snippet. JSON validation, header dedup, body shapes (raw / JSON / multipart / url-encoded). Pure client-side, no upload.

Shortcut: hrbh

Validate a commit message against the Conventional Commits v1.0.0 spec. Live checks on type, scope, subject length and form, body, footers, and the BREAKING CHANGE marker; configurable rules; reformat to canonical form; one-click presets for feat / fix / BREAKING / chore / revert. Pure client-side, no upload.

Shortcut: cclc

Paste any phone number and see the country, calling code (200+ countries), and national number, formatted as E.164 (+141****2671), international (+1 415 555 2671), or national (415) 555-2671). Validates against the E.164 plan for that country, best-effort guesses a line type (mobile / landline / unknown) from country-specific mobile prefixes. Single input or bulk, copy / download as TSV. Pure client-side, no upload.

Shortcut: pnpf

Paste a JSON document and a JSONPath expression; see every match with its full path, copy paths or values, browse a preset library, and read a one-page cheat-sheet of the supported syntax. Supports $, .key, ..recurse, [*], [n], [n:m], [n,m,...], and [?(@.field op value)] filters. Pure client-side, no upload.

Shortcut: jejs

Paste an SVG path-data string and watch it draw live. Total path length, bounding box, per-command breakdown (M, L, H, V, C, S, Q, T, A, Z), stroke and fill controls, optional grid, and a reference table for all ten path commands. Pure client-side, no upload.

Shortcut: spvs

Escape or unescape a string for seven contexts: JavaScript string literal, JSON string (RFC 8259), HTML / XML (xml-safe, named, all, decimal, hex modes), SQL (single-quoted), POSIX shell (single-quoted), Python repr, and CSS string. Live as you type, copy-ready output, decode errors report the offset, four contexts round-trip. Pure client-side, no upload.

Shortcut: sest

Compute HMAC-SHA-1, HMAC-SHA-256, HMAC-SHA-384, or HMAC-SHA-512 of any message with a secret key in your browser. Web Crypto, hex or base64 output, key as text or hex, optional expected-digest verify with constant-time compare. Five common API presets (GitHub, Stripe, Slack, AWS SigV4, OAuth 1.0a). Pure client-side, the key never leaves your browser.

Shortcut: hghm

Compose a 5-field cron expression by clicking through a friendly picker — Every / Every Nth / Specific minutes / Range — for each of minute, hour, day-of-month, month, and day-of-week. Live plain-English summary, next 10 runs in your local time, an Import mode that decodes any cron back into the picker, and 12 common presets. Pure client-side, no upload.

Shortcut: cebc

Validate a JSON value against a JSON Schema in your browser. Type checks, length and range constraints, required properties, $ref, anyOf / oneOf / allOf / not, and the common string formats (email, uuid, ipv4, date, …). Structured error list with JSON Pointers, fail-fast toggle, copy errors as TSV. Pure client-side, no upload.

Shortcut: jsvj

Identify an unknown hash, checksum, address, or token by length, character set, and any known prefix. Detects MD5, SHA-1, SHA-2, SHA-3, BLAKE, bcrypt, Argon2, NTLM, JWT, UUID, Bitcoin, Ethereum, IPFS CID, and 50+ other formats with confidence levels. Pure client-side, no upload.

Shortcut: hiha

Paste any UUID and see its version (1–8, NIL, MAX), variant (RFC 4122, Microsoft legacy, NCS, future), and — for time-based versions — the embedded timestamp in unix ms and human UTC. Canonical, braced, URN, hex, and base64 forms. Pure client-side, no upload.

Shortcut: uidu

Build a CSS @keyframes animation with a live preview on a sample element. Pick a name, duration, timing function, iteration count, direction, fill mode, and delay; edit the keyframe stops; copy the ready-to-paste @keyframes block and the shorthand animation property. Pure client-side, no upload.

Shortcut: cagc

Resolve an RFC 6901 JSON Pointer against any JSON document in your browser. Live evaluation, syntax-highlighted result, 12 presets, copy buttons, and a one-page cheat-sheet covering escapes, the /- append sentinel, and array indices. Pairs with the JSONPath tool for JSON Patch (RFC 6902). Pure client-side, no upload.

Shortcut: jpej

Drop any file and get SHA-1, SHA-256, SHA-384, and SHA-512 digests computed in your browser via Web Crypto. Verify against an expected checksum or a sha256sum-style sidecar file (constant-time compare, case-insensitive, whitespace-tolerant, sha256: prefix stripped). The file never leaves your device. Pure client-side, no upload.

Shortcut: fhcv

Visual CSS border-radius builder. Each of the four corners has a horizontal and a vertical axis, so you can shape circles, ellipses, leaves, eggs, blobs, squircles, and arbitrary squished shapes. Twelve shape presets, live preview, copy-ready CSS in the shortest correct form (1, 4, 8 values or the slash-ellipse form). Pure client-side, no upload.

Shortcut: cbrg

Paste a cron expression and see a 7-day by 24-hour heatmap of when it will fire. Density per day and per hour, next 10 runs, busiest hour and day, eight preset expressions. Pure client-side, no upload.

Shortcut: cshc

Parse a .env file in your browser and see every key with its kind and any linter findings. Re-export as .env.example (with secret redaction), JSON, YAML, shell export, docker-compose, or Dockerfile ENV. Pure client-side, no upload.

Shortcut: eplf

Diff two CSV, TSV, or pipe-delimited files in your browser. Row-level added / removed / changed / unchanged with cell-level per-column diffs inside each changed row. Optional composite-key column alignment, header-mismatch warning, copy as CSV patch or unified-diff plain text, download as .csv. Pure client-side, no upload.

Shortcut: cdcs

Drop a file, paste raw bytes, or open a built-in example and see a classic hex-dump view (offset · bytes · printable-ASCII column). Stats panel with size, Shannon entropy, top bytes, and detected file format (magic-byte signature for PNG, JPEG, ZIP, ELF, …). Hex-pattern search with ?? wildcards. Pure client-side, no upload.

Shortcut: hfih

Build CSS text-shadow values with a live preview. Up to 6 layers (offset, blur, colour), presets for Soft / Hard / Long Shadow / Glow / Vivid Glow / Outline / 3D Pressed / Vintage. Copy-ready output in rgba, rgb, hex, or hexa. Pure client-side, no upload.

Shortcut: ctsg

Paste JavaScript and get a javascript: URL you can drag to your bookmarks bar. Live length meter (2k / 8k / 32k thresholds), four built-in helpers ($, $$, qs, DOMContentLoaded), conservative minifier, copy URL or link HTML, and a sandboxed iframe test runner. Pure client-side, no upload.

Shortcut: bbok

Compose a robots.txt in your browser from a curated catalog of 36 known bots — search engines, AI crawlers, social previewers, SEO tools, uptime monitors, and shopping bots. Per-bot Allow all / Block all / Custom rules, sitemaps, optional Yandex-style Host directive, optional per-bot Crawl-delay. Live preview with lint, import existing robots.txt to seed the picker, copy or download. Pure client-side, no upload.

Shortcut: rgro

Paste a Markdown document with YAML frontmatter (Hugo, Jekyll, Eleventy, Astro) and get a structured view of every field with type, value preview, line number, JSON dump, raw YAML, and the markdown body. Built-in linter for unclosed fences, non-mapping roots, case-insensitive duplicate keys, empty keys, and bad date values. Pure client-side, no upload.

Shortcut: mfpf

Paste any CSS @supports condition and see whether the current browser matches it. Live breakdown of every sub-condition, a curated reference table for declarations, selector(), font-tech(), and font-format() probes, and copy-ready canonical form. Pure client-side, no upload.

Shortcut: csts

Minify HTML in your browser: strip comments, collapse whitespace, drop optional closing tags, drop default and boolean attribute values. Toggle any option off, see live byte savings, and copy the result. Pretty-print mode is the inverse — re-introduce indentation on every block-level tag. Pure client-side, no upload.

Shortcut: hmpp

Audit every <a> tag in a chunk of HTML. Detects missing hrefs, empty link text, target=_blank without rel=noopener, javascript: schemes, malformed mailto:/tel:, duplicate hrefs, and long URLs. Pure client-side, no upload.

Shortcut: hlch

Parse a Set-Cookie header or a document.cookie string in your browser. See name, value, and every attribute (Domain, Path, Expires, Max-Age, Secure, HttpOnly, SameSite). Lints RFC 6265 mistakes — bad SameSite, missing Secure on __Host- / __Secure- prefixed names, non-integer Max-Age, bad Expires date. Generate a canonical Set-Cookie from a form. Pure client-side, no upload.

Shortcut: hcpg

Paste a URL or hostname and walk every subdomain label back to its registrable domain (eTLD+1). 80+ multi-part public suffixes including .co.uk, .com.au, .co.jp, .com.br. Detects IPv4 and IPv6 literals. Bulk mode, copy as TSV. Pure client-side, no upload.

Shortcut: sesu

Validate ISBN-10 or ISBN-13 in your browser. mod-11 (X) and mod-10 checks, group / registrant / publication split, ISBN-10 ↔ ISBN-13 conversion. Bulk mode, TSV export. Pure client-side, no upload.

Shortcut: ivis

Paste an NDJSON / JSON Lines stream and see each line parsed with line number, validity, pretty-printed value, and a JSONPath column. Filter by kind, substring search, dotted-path + wildcard JSONPath, copy as NDJSON or JSON array, download .ndjson. Pure client-side, no upload.

Shortcut: jlnv

Compose a CSS filter chain visually. Ten filter functions (blur, brightness, contrast, drop-shadow, grayscale, hue-rotate, invert, opacity, saturate, sepia), live preview on a sample image, eleven curated presets, paste-any-value import, copy-ready CSS. Pure client-side, no upload.

Shortcut: csgc

Look up a file extension to find its MIME / content type, or reverse-lookup a MIME string to see every extension that uses it. Searchable database of 220+ IANA-registered and vendor types, with RFC 6838 syntax validation. Pure client-side, no upload.

Shortcut: mtlm

Paste HTTP response or request headers, get a per-line parse and a security lint (HSTS, CSP, X-Content-Type-Options, X-Frame-Options, CORS, info-disclosure, deprecated headers). Look up any header in a curated catalogue of 75+ IANA, vendor, and deprecated headers, with category and kind filters. Pure client-side, no upload.

Shortcut: hhih

Live ticking Unix clock showing the current epoch in 8 forms (milliseconds, seconds, hex, ISO 8601 UTC, ISO 8601 local, RFC 2822, Swatch Internet Time, ISO week, day-of-year) plus a converter panel that parses any user-typed epoch form. Accepts decimal (10/13/16/19 digits auto-detect s/ms/us/ns), 1.5s / 1234ms / 1000us / 1000000ns suffixes, 0x hex, and any ISO 8601 / RFC 2822 string. Pure browser, no upload.

Shortcut: ucun

Look up American Wire Gauge (AWG) diameter, cross-section, and DC resistance, or convert mm² to the nearest AWG. 44-entry reference table from AWG 0000 (4/0) to AWG 40 with diameter in mm and inches, area in mm² and circular mils, resistance in Ω/km and Ω/1000ft, and a chassis-wiring ampacity hint. Accepts AWG 14, AWG 12, 4/0, 0000, etc. Copper at 20°C. Pure browser, no upload.

Shortcut: wgcw

Build an RSS 2.0 or Atom 1.0 feed in your browser. Type the channel title, link, description, language, and TTL, add items with title, link, description, pubDate, optional GUID, author, and categories. Live preview, copy to clipboard, download as .xml. Proper XML escaping and RFC 2822 / ISO 8601 dates. Pure client-side, no upload.

Shortcut: rfbr

Inspect a fetch request: see whether the browser will fire a CORS preflight, view the OPTIONS the browser would send on the wire, paste back the response headers, and get a pass/fail checklist with one-line fixes (Allow-Origin, Allow-Methods, Allow-Headers, Allow-Credentials, Vary: Origin). Pure client-side, no upload.

Shortcut: cpic

Build a Content-Security-Policy header or meta tag in your browser. 24 directives (default-src, script-src, object-src, base-uri, frame-ancestors, and more), live source-list validation per CSP3, quick-insert for nonces and inline-script sha256 hashes, parse an existing CSP into the editor, copy as header or meta tag. Pure client-side, no upload.

Shortcut: cgcs

Look up any ASCII or Unicode code point: char, hex, dec, oct, bin, JavaScript escape, Unicode name. 1,000+ entry reference table across ASCII, Latin-1 Supplement, punctuation, currency, arrows, math, box drawing, weather / sports / zodiac symbols, dingbats, CJK, fullwidth, and curated emoji. Round-trip strings to code points. Pure client-side, no upload.

Shortcut: aucp

Collapse overlapping and adjacent IPv4 CIDR blocks into the minimal disjoint supernet set. Paste one CIDR per line, see per-line validation, the coalesced result, total addresses, and total usable hosts (RFC 3021 /31). Pure client-side, no upload.

Shortcut: crmc

Assemble a URL from typed parts: scheme, host, port, path, query rows, fragment. Toggle per-component RFC 3986 percent-encoding or paste an existing URL to edit it. Live, in your browser, no upload.

Shortcut: ubur

Minify JavaScript by stripping comments, collapsing whitespace, and dropping trailing semicolons. Or pretty-print with a configurable indent. Live byte savings, in your browser, no upload.

Shortcut: jmfj

Read the wall-clock time as a 6×4 BCD grid in your browser. Live auto-tickling display, manual HH:MM:SS entry, hex and decimal-hour readouts, copy-ready ASCII pattern. Pure client-side, offline.

Shortcut: bcbi

Read the wall-clock time as a 6-digit hex colour (#HHMMSS) in your browser. Live ticking swatch, manual entry or hex paste, RGB / HSL / luminance / WCAG contrast readouts, closest CSS named colour. Pure client-side, offline.

Shortcut: hche

Compute CRC-8, CRC-16-CCITT, CRC-32, Adler-32, Fletcher-16, one's-complement byte sum, and XOR-8 checksums on text or files in your browser. Hex + decimal output, preset test vectors, copy per row, no upload.

Shortcut: cche

Paste any stack trace from Node, V8, Chrome, Firefox, Safari, Java, Python, Go, or Rust and see every frame parsed (function, file, line, column) and classified (call, init, eval, async, global). Re-render runtime-native or as a Markdown list for chat paste. Pure client-side, no upload.

Shortcut: stfs

Compose any Cache-Control HTTP header value in your browser. Toggle the directives that matter (max-age, public, private, no-store, no-cache, immutable, stale-while-revalidate, …), paste an existing header to load it back into the editor, pick from twelve common presets with a one-paragraph rationale, and read per-directive explanations straight from RFC 9111. Pure client-side, no upload.

Shortcut: cchb

Pretty-print, minify, and validate any XML document in your browser. RSS, Atom, sitemap.xml, SOAP envelopes, OpenAPI, Web App Manifest, and more. Indent with 2 spaces, 4 spaces, or a tab; sort attributes; strip the XML declaration, DOCTYPE, comments, or processing instructions; collapse text whitespace; live errors at line and column. Pure client-side, no upload.

Shortcut: xfmv

Convert between MIDI note number, frequency in Hz, note name (A4, C#5, Bb3, F♯4), and signed cents deviation in your browser. 12-tone equal temperament with A4 = 440 Hz, sharps or flats spelling, interactive one-octave piano roll, per-octave reference table, configurable A4 reference for 432 Hz tuning. Pure client-side, offline.

Shortcut: nfcn

Find the best UTC overlap window across 2-6 time zones in your browser. Per-participant working hours, optional lunch, configurable working days, colour-coded 7×24 heatmap, copy-ready summary, and per-cell local-time details. Pure client-side, offline.

Shortcut: mtof

Look up the registered vendor (IEEE OUI / MA-M / MA-S) for any MAC address in your browser. Accepts every common format (colon, hyphen, Cisco dot, plain). Per-vendor note and country, plus the IEEE 802 I/G and U/L tag bits. Bulk mode (one per line) with copy-as-TSV. Pure client-side, no upload.

Shortcut: mvol

Tap a key or click to measure tempo in beats per minute, then play a metronome click with time signatures, subdivisions, and a humanize jitter. Median-filtered tap detection (last 8 intervals), eight time signatures (4/4, 3/4, 2/4, 6/8, 9/8, 12/8, 5/4, 7/8), eight tempo presets (Grave → Prestissimo), Web Audio click, stability indicator. Pure client-side, no upload, no tracking.

Shortcut: bttm

Preview exponential-backoff retry schedules with full jitter, equal jitter, decorrelated jitter, or a deterministic baseline. Adjust base, cap, attempts, and factor; the table shows per-attempt delay, cumulative time, and the random draw window. Export the schedule as TSV, JSON, or a copy-paste JavaScript function for the strategy you picked. Pure client-side, no upload, no tracking.

Shortcut: ebcb

Generate and verify bcrypt password hashes ($2a$, $2b$, $2y$) in your browser. Cost 4–14 slider, random or typed 16-byte salt, bulk mode, copy as TSV / JSON. The output is the standard 60-char bcrypt string compatible with PHP password_hash, Node bcrypt, Python bcrypt, Go x/crypto/bcrypt, and jBCrypt. Pure-JS implementation, no upload, no tracking.

Shortcut: bhgv

Twelve bitwise operations (AND, OR, XOR, NOT, NAND, NOR, XNOR, logical and arithmetic shifts, rotations) over 8/16/32/64-bit widths. Live bit-grid with per-bit color, popcount, leading and trailing zero counts, signed two's-complement view, hex/bin/dec/oct outputs. BigInt math throughout so 64-bit values stay exact. Pure client-side, no upload.

Shortcut: bibi

Test primality, factorise integers into primes, sieve a range, and look up the n-th prime in your browser. Includes divisor count, Euler's totient, Möbius function, and next/previous prime lookup. No upload.

Shortcut: pnff

Generate a properly commented license header for a source file. Choose from 16 SPDX license templates, set the year and copyright holder, and infer the comment style from the filename. Pure client-side, no upload.

Shortcut: lhgl

Paste a regular expression and see every token explained in plain English — anchors, character classes, quantifiers, groups (capturing, named, lookaround), alternation, backrefs, Unicode properties. Textbook catastrophic-backtracking shapes are flagged. Live test against a sample string so the explanation and the actual matches stay in lockstep. Pure client-side, no upload.

Shortcut: rere