All tools
Browse every LocalTools utility in one place. For topic-focused discovery, see our curated collections: JSON & data formats, text utilities, and security tools — or open the complete list below.
JSON Tools
- JSON Formatter & ValidatorFree online JSON formatter and validator. Beautify, minify, and validate JSON data. 100% client-side processing - your data never leaves your browser.
- JSON ↔ YAML converterConvert between JSON and YAML in your browser with line/column errors. Data never leaves the device.
- JSON to TypeScriptTurn a JSON sample into TypeScript interfaces or type aliases in your browser. Data stays on the device.
- JSON MinifierRemove whitespace from JSON and validate in one step—all in your browser. Focused workflow separate from prettifying.
- JSONPath evaluatorRun JSONPath queries on JSON in your browser—view matching values or each match’s path. No upload.
- JSON Schema validatorValidate a JSON instance against a JSON Schema in your browser—Ajv drafts 07 / 2019-09 / 2020-12. No upload.
- XML formatterPretty-print or minify XML in your browser with DOMParser validation and a local serializer.
- HTML formatter & minifierPretty-print or minify HTML snippets and documents in your browser with DOMParser and a local serializer.
- TOML formatter & validatorFormat TOML and surface parse errors with @iarna/toml in your browser. Copy or download formatted.toml—local only.
- .env file editorParse, validate, normalize, and merge .env files in your browser. Duplicate keys, POSIX hints, and export lines—copy or download locally.
- INI / Java properties ↔ JSONConvert INI or Java `.properties` text to JSON and back in your browser—sections, comments, and continuations parsed locally.
Converters
- CSV to JSON / HTML / MarkdownParse CSV in your browser with auto-detected delimiters. Export as JSON (objects or arrays), sortable HTML tables, or GitHub-ready Markdown. Nothing is uploaded.
- URL Encoder & DecoderEncode or decode URL components with encodeURIComponent / decodeURIComponent or encodeURI / decodeURI, and parse full URLs into parts — all locally in your browser.
- HTML EntitiesEscape and unescape HTML entities (&, <, numeric and named) in your browser — for snippets, attributes, and safe text.
- Hex Encoder & DecoderConvert text to UTF-8 hex and hex dumps back to text, with a byte view — all in your browser.
- MIME Type LookupSearch a curated table of file extensions and MIME types. Filter by category, copy values, and see common extensions for a MIME string — all offline in your browser.
- Percentage CalculatorPercent change, “X is what % of Y”, and tip/tax math — delta, markup, and reverse totals — in your browser.
- Big Number CalculatorArbitrary-precision integer and decimal math — add, multiply, divide, power, sqrt — beyond JavaScript Number limits, in your browser.
- Unit ConverterConvert length, mass, temperature, and data-size units — metric, imperial, SI decimal, and binary IEC prefixes — in your browser.
- Radix & Base ConverterConvert integers between bases 2–36 — binary, octal, decimal, hex, and custom radices — with BigInt precision in your browser.
- Unix timestamp converterConvert Unix epoch seconds or milliseconds to UTC and local calendar time, or parse ISO and other date strings back to epoch — all in your browser.
- Timezone converterCompare IANA timezones for one instant: offsets, abbreviations, and local wall-clock strings using your browser’s Intl data — no network calls.
- Date difference calculatorMeasure the duration between two datetimes: exact day/hour breakdown, calendar years/months/days, and totals — all in your browser.
- ISO 8601 parserParse ISO 8601 date and datetime strings into year/month/day, offsets, week and ordinal dates, and Unix epoch — all in your browser.
- CSS Unit Converter & Fluid TypeConvert px, rem, em, vh, vw, and %; build linear clamp() for fluid type; convert HEX, RGB, and HSL — all in your browser with live previews.
- Color converterConvert colors between HEX, RGB, HSL, and OKLCH with a live swatch — all in your browser.
- WCAG contrast checkerCheck foreground and background colors for WCAG 2.x contrast ratio and AA/AAA pass levels — in your browser.
- CSS box-shadow generatorBuild layered box-shadow CSS with a live preview and copy-ready declaration — in your browser.
- CSS border-radius generatorTune eight corner radii (horizontal and vertical per corner) with a live preview and copy-ready CSS — in your browser.
- CSS animation timing editorDesign cubic-bezier and steps timing functions with a draggable curve preview and copy-ready CSS — in your browser.
- Tailwind class mergerMerge conflicting Tailwind CSS utility classes with tailwind-merge — dedupe padding, colors, and responsive variants locally.
Developer Tools
- GraphQL formatterPretty-print or minify GraphQL queries, mutations, and SDL with graphql.js parse/print in your browser.
- Port Number ReferenceSearch a bundled table of common well-known ports by number, service, protocol, and category. Filter and copy values locally with no network calls.
- UUID GeneratorGenerate RFC 4122 version 4 UUIDs and the nil UUID in your browser. Batch up to 500 and copy in one click.
- ULID GeneratorCreate sortable identifiers with an embedded millisecond timestamp. Decode any ULID to UTC, local time, and randomness.
- NanoID GeneratorCreate compact, URL-friendly IDs with adjustable length and alphabet presets—or your own character set. Batch up to 500; all randomness stays local.
- Random String GeneratorGenerate cryptographically random passwords and tokens: pick character classes, exclude ambiguous symbols, require coverage, and batch up to 500 — all in your browser.
- JWT DebuggerDecode and inspect JWT payloads in your browser — no upload. Sign test tokens with HMAC; secrets stay on your device.
- SVG to JSXOptimize SVG with SVGO in a Web Worker, then turn it into a React component with camelCase attributes. Everything stays in your browser.
- Cron GeneratorBuild and verify crontab schedules with a visual grid or raw expression. Human-readable explanations and next run times—all in your browser.
- QR Code StudioCreate and scan QR codes for URLs, text, Wi-Fi, and contacts. Customize colors, error correction, and quiet zone. Export PNG, SVG, or WebP — all in your browser.
- Browser AuditorSee what your browser exposes: hardware, WebRTC, canvas/WebGL/audio fingerprints, fonts, and screen — scored locally with no tracking.
- Code Snap StudioTurn snippets into syntax-highlighted images (Carbon-style) for docs and social posts. Pick language, theme, window chrome, padding, and background — export PNG, SVG, or copy to clipboard, all locally.
- Subnet CalculatorIPv4/IPv6 subnet math: CIDR, masks, network and broadcast (IPv4), usable hosts, wildcard mask, binary view, and IP classification — 100% in your browser.
- Password Strength & EntropyMeasure entropy, zxcvbn strength, and estimated crack times across hardware tiers — 100% offline in your browser.
- Multi-Hash & Base64 FactoryEncode text to Base64, hex, URL, and HTML entities; compute SHA-256, SHA-512, SHA-1, and MD5 — all live in your browser. Drop a file for a local SHA-256 checksum.
- RegEx StudioVisual regex tester with live highlights, capture groups, explanations, and code snippets. Runs entirely in your browser.
- SQL Formatter StudioFormat SQL for PostgreSQL, MySQL, SQLite, and T-SQL, minify for production strings, and design CREATE TABLE scripts with a visual schema builder — all in your browser.
- Cloud Resource Cost EstimatorCompare AWS, Azure, and GCP compute SKUs against your target vCPU and RAM, model SSD/HDD/cold storage, and convert estimates into global currencies — instantly in your browser.
- PKI & Certificate StudioGenerate RSA and ECC keys, build CSRs and self-signed certificates, and inspect PEM chains — all locally in your browser.
- HMAC & Webhook VerifierGenerate and verify HMAC signatures (SHA-256, SHA-512, SHA-1, MD5) for webhook bodies — hex or Base64, entirely in your browser.
- TOTP ToolGenerate a TOTP secret, show an otpauth QR for authenticator apps, display the live code, and verify codes with Web Crypto — all locally.
- AES-GCM encrypt / decryptEncrypt or decrypt text and files with AES-128/192/256-GCM in your browser: paste hex key and IV, optional AAD, Web Crypto only.
- RSA key generatorGenerate RSA public/private key pairs in your browser with Web Crypto; export PKCS#8 private and SPKI public PEM.
- PEM decoderSplit PEM text into labeled Base64 payloads and DER byte lengths in your browser — pairs with PKI and RSA tools.
- HKDF & PBKDF2 playgroundDerive keys from a passphrase or IKM with visible salt, info, iterations, and hash — Web Crypto in your browser.
- curl to fetch converterPaste a curl command and get JavaScript fetch() code — headers, method, and body preserved. Runs locally; your command never leaves the browser.
- OpenAPI snippet validatorValidate OpenAPI 3.x or Swagger 2.0 YAML/JSON snippets in your browser—structural checks with path-level errors. No upload.
- JWT test token generatorGenerate signed HS256/384/512 test JWTs with auto iat and exp claims in your browser. Secrets stay local — for API debugging only.
- Webhook payload formatterPretty-print or minify JSON webhook bodies and browse common provider signature headers — all locally in your browser.
- User agent parserBreak down HTTP User-Agent strings into browser, OS, device, engine, and bot signals — parsed locally with no external lookups.
- MAC address formatterNormalize MAC/EUI addresses and look up IEEE OUI vendors — colon, hyphen, Cisco dot, and bare hex — fully offline.
- CIDR aggregatorMerge overlapping and adjacent CIDR blocks into a minimal route list — IPv4 and IPv6, fully offline.
- IP in CIDR checkerBulk-check IP addresses against an allow/deny CIDR list — IPv4 and IPv6, fully offline.
Image Tools
- Image OptimizerCompress, resize, and convert images (PNG, JPG, WebP) locally. 100% client-side processing - your images never leave your browser.
- Image to Base64Convert PNG, JPEG, WebP, GIF, and SVG images to Base64 data URLs with MIME type and size estimates — entirely in your browser.
- Favicon GeneratorTurn a PNG or JPEG into a multi-size favicon.ico plus Apple/Android PNG pack — resized and packaged entirely in your browser.
- SVG MinifierOptimize and minify SVG with SVGO in a Web Worker—safe, balanced, or aggressive profiles with byte savings and live preview. Everything stays in your browser.
Text Tools
- Markdown table formatterAlign GitHub-flavored markdown pipe tables and optionally sort data rows by column — all in your browser.
- AsciiDoc previewLive AsciiDoc → HTML preview with copy and download — @asciidoctor/core runs entirely in your browser.
- Mermaid live editorLive Mermaid diagram preview with SVG and PNG export — mermaid.js runs entirely in your browser.
- Secret ShareSeal text with AES-GCM and a master password. Share a single link where ciphertext and IV live in the URL hash — nothing is stored on a server.
- Diff CheckerCompare two texts with character, word, or line diff — side-by-side or inline. Ignore whitespace, swap sides, sync-scrolled panes. 100% local in your browser.
- Text statisticsCount words, characters, lines, paragraphs, and rough sentences; estimate reading time from a configurable speed — all in your browser.
- Text case converterTurn phrases and identifiers into camelCase, PascalCase, snake_case, kebab-case, and CONSTANT_CASE using local heuristics — choose one phrase per box or one conversion per line — nothing is uploaded.
- SlugifyBuild URL- and file-friendly slugs from titles in your browser: Unicode-safe or Latin ASCII folding, hyphen or underscore separators, optional one-slug-per-line — nothing is uploaded.
- Sort linesSort, reverse, or randomly shuffle lines from pasted text in your browser — optional locale-aware numeric sorting and case rules — nothing is uploaded.
- Dedupe linesRemove duplicate lines from pasted text in your browser — keep first occurrences or sort unique lines with locale-aware ordering — nothing is uploaded.
- Find & Replace (batch)Multiline find and replace in your browser — literal text (with optional case rules) or JavaScript regex with flags; replacement counts and copy — nothing is uploaded.
- Lorem Ipsum generatorCreate paragraphs, exact word counts, or Markdown-style bullet lists of placeholder Latin in your browser — tunable sentences, optional classic opening, regenerate with Web Crypto randomness — nothing is uploaded.
- Whitespace normalizerNormalize line endings (LF / CRLF), expand tabs to spaces or compress leading spaces to tabs, and strip trailing spaces — all in your browser with live stats — nothing is uploaded.
- Levenshtein distanceCompare two strings with classic edit distance (insert, delete, substitute) and an optional dynamic-programming matrix — computed locally in your browser.
- Markdown StudioLive GFM Markdown editor with preview, auto-format, HTML export, and rich-text copy. 100% client-side.
- Web Font & Typography WorkbenchPair heading and body fonts, build modular scales, tune variable axes, preview CLS-safe fallbacks, and export CSS — all in your browser.