# DevKit — Local-First Developer Tools

A browser-based, zero-upload toolbox of 107 developer utilities that run entirely on-device — no login, no tracking, no server round-trip. Every tool processes your input locally.

## Tools by category

### DATA & PROCESS
- JSON Formatter: Validate and beautify JSON with precise line-and-column error reporting; minify to a single line in one click. — https://dev.miaokit.tech/t/json
- Timestamp Converter: Convert timestamps to dates and back; auto-detects 10-digit seconds and 13-digit milliseconds, with time zones and relative time. — https://dev.miaokit.tech/t/ts
- Regex Tester: Real-time matching with per-group highlighting and capture-group breakdown; empty matches are skipped automatically so complex patterns are safe to test. — https://dev.miaokit.tech/t/regex
- Text Stats: Live character, word, line and UTF-8 byte counts; mixed CJK/English text is counted per han character and per whole word. — https://dev.miaokit.tech/t/text
- Case Converter: One-click conversion between UPPER, lower, Title, camelCase, snake_case and kebab-case — stop retyping field names. — https://dev.miaokit.tech/t/case
- Full/Half Width Converter: Two-way full-width ↔ half-width conversion with automatic ASCII offset; great for cleaning "wide" characters copied from Word or chat apps. — https://dev.miaokit.tech/t/fw
- Thousand Separator: Add or remove thousands separators for long numbers, negatives and decimals included — amounts and big numbers read at a glance. — https://dev.miaokit.tech/t/num
- Text Diff: Two-pane text comparison in line or character mode with green-add / red-remove highlighting — spot every change instantly. — https://dev.miaokit.tech/t/diff
- CSV ⇄ JSON Converter: Two-way CSV ↔ JSON conversion that handles commas and newlines inside quoted fields, with delimiter and header options. — https://dev.miaokit.tech/t/csv
- Cron Parser: Parse 5/6-field cron expressions into plain-language descriptions and upcoming run times, with range validation. — https://dev.miaokit.tech/t/cron
- JSON Tree Viewer: Render JSON as a collapsible hierarchy tree — deep nesting becomes readable at a glance, with precise error locating. — https://dev.miaokit.tech/t/jtree
- JSON ⇄ YAML / XML: Four-way conversion between JSON, YAML and XML (with attribute and text-node conventions) — API debugging and config migration in one place. — https://dev.miaokit.tech/t/jconv
- Line Tools: Batch line operations: trim whitespace, delete empty lines, order-preserving dedupe and sorting, freely combined — a cleanup tool for lists and logs. — https://dev.miaokit.tech/t/lines
- HTTP Status Codes: A quick reference of 60 common HTTP status codes with meanings and category filters — stop digging through docs when debugging APIs. — https://dev.miaokit.tech/t/http
- JSONPath Query: Extract and filter JSON locally with JSONPath expressions — recursive descent, slices and conditional filters; matched values and paths side by side. — https://dev.miaokit.tech/t/jsonpath
- Math Expression Evaluator: Evaluate math expressions safely — + - * / % ^, parentheses, functions (sin / sqrt / log…) and constants, with live results and readable errors. — https://dev.miaokit.tech/t/math
- Set Operations: Treat lines of text as sets: intersection, union, difference, dedupe and duplicate detection at line level, with optional whitespace and case folding — compare two lists the easy way. — https://dev.miaokit.tech/t/setops
- Text Extractor: Pull URLs, emails, IPs, phone numbers, hashes and dates out of any text in bulk — categorized, deduped and copied in one click; stop hand-picking from logs and traffic dumps. — https://dev.miaokit.tech/t/extract
- JSON Schema Builder & Validator: Infer a draft-07 schema from a JSON sample, then validate data against it — errors pinpointed to JSON Pointer paths, common keywords covered, fully local. — https://dev.miaokit.tech/t/jsonschema
- JSON Repair: One-click repair of broken JSON — single quotes, unquoted keys, trailing commas, // and /* */ comments, smart quotes and truncation become valid JSON, with precise locations when unfixable. — https://dev.miaokit.tech/t/jsonrepair
- JSON ⇄ JSONL Converter: Convert between JSON arrays and NDJSON (one JSON per line) in both directions, validating line by line and flagging bad line numbers; handles large text with a 10MB batching hint. — https://dev.miaokit.tech/t/jsonl
- JSON Diff: Semantic diff of two JSON documents — ignores key order and whitespace, with a tree view flagging added / removed / changed nodes; optionally ignore array order or string case. — https://dev.miaokit.tech/t/jsondiff

### ENCODE & SECURITY
- Base64 Encode / Decode: UTF-8-safe Base64 encoding and decoding — no garbled CJK text; independent encode and decode panels that never interfere. — https://dev.miaokit.tech/t/base64
- URL Encoder / Decoder: Two-way encodeURIComponent / decodeURIComponent with full URL breakdown into protocol, host, path and query params. — https://dev.miaokit.tech/t/url
- Hash Calculator: Real-time SHA-1 / 256 / 384 / 512 digests computed locally with WebCrypto — perfect for verifying file fingerprints. — https://dev.miaokit.tech/t/hash
- JWT Decoder: Split a three-part token into header algorithm, payload claims and expiry at a glance. Decode only — no signature verification. — https://dev.miaokit.tech/t/jwt
- Base Converter: Convert between any base (2–36), integers and fractions alike — handy for memory addresses, color values and protocol fields. — https://dev.miaokit.tech/t/base
- HTML Entity Encoder / Decoder: Escape < > & " ' to entities or restore &lt;div&gt; and &#65; back to text — a staple for debugging front-end templates. — https://dev.miaokit.tech/t/html
- MD5 & HMAC: Compute MD5 and HMAC-MD5 digests fully offline, with CJK text and arbitrary keys — handy for file fingerprints and legacy API signatures. — https://dev.miaokit.tech/t/md5
- QR Code Reader: Decode QR codes from an image locally — large images are auto-scaled for recognition; nothing is ever uploaded. — https://dev.miaokit.tech/t/qrscan
- File Hash Checker: Drop a file to compute MD5 and SHA-1/256/384/512 digests locally — zero bytes uploaded; instantly tell if a download is intact. — https://dev.miaokit.tech/t/filehash
- Unicode Escape Converter: Convert CJK text and Emoji to \\uXXXX escapes or restore them, auto-merging surrogate pairs — turn mojibake in API logs readable in a second. — https://dev.miaokit.tech/t/unicode
- URL Parameter Editor: Parse every part of a URL and edit query params in a table — change values, delete or add params and rebuild the link live, with auto-encoding. — https://dev.miaokit.tech/t/urlparse
- JSON Escape / Unescape: Escape text containing quotes, newlines and backslashes into a form safe to embed in JSON, or restore it — handy when writing fixtures and string literals. — https://dev.miaokit.tech/t/jsonescape
- HMAC Signature Generator: Compute HMAC signatures with SHA-1/256/384/512 — key and message in, WebCrypto computes locally, hex or base64 out. — https://dev.miaokit.tech/t/hmac
- AES Encryption: AES-GCM encryption and decryption via WebCrypto with key and IV input, supporting base64 or hex for both text and ciphertext — sensitive data never leaves the browser. — https://dev.miaokit.tech/t/aes
- htpasswd Generator: Generate Apache htpasswd entries in bcrypt, apr1 (MD5) or SHA-1 format, hashing passwords locally — handy for Nginx and Basic Auth setups. — https://dev.miaokit.tech/t/htpasswd
- X.509 Certificate Parser: Paste a PEM certificate to read subject, issuer, validity, serial number and public-key algorithm, with days-left and expiry status — ideal for debugging HTTPS and certificate chains. — https://dev.miaokit.tech/t/certparse
- HTML Entity Reference & Escape: A reference of 120+ named entities (filterable live, click to copy) plus batch escape/unescape of whole text blocks, with optional named-entity output for non-ASCII. — https://dev.miaokit.tech/t/htmlescape
- Bcrypt Hash: Generate and verify Bcrypt password hashes ($2b$…) locally with a 4–15 cost factor; hashing and verification both run on-device, passwords never uploaded. — https://dev.miaokit.tech/t/bcrypt
- RSA Key Pair Generator: Generate RSA key pairs locally in your browser (2048/3072/4096), exporting both PEM (SPKI public / PKCS8 private) and JWK; keys never leave the device and touch no server. — https://dev.miaokit.tech/t/rsa
- TOTP Authenticator: Local TOTP codes per RFC 6238 (HMAC-SHA1, refreshed every 30s) with multiple accounts and QR import; keys are stored only on this device — avoid shared computers. — https://dev.miaokit.tech/t/totp

### GENERATORS
- UUID Generator: Generate batches of cryptographically secure UUID v4; optional uppercase and hyphen stripping, one click for another batch. — https://dev.miaokit.tech/t/uuid
- Password Generator: Generate strong passwords locally: pick length and character sets, exclude look-alikes; live entropy-based strength meter. — https://dev.miaokit.tech/t/pwd
- Random String Generator: Generate random strings locally with configurable length, character set and look-alike exclusion — great for test data and throwaway tokens. — https://dev.miaokit.tech/t/rand
- Lorem Ipsum Generator: Generate standard Lorem Ipsum placeholder text with adjustable paragraphs and sentences per paragraph — fill prototypes in one click. — https://dev.miaokit.tech/t/lorem
- Mock Data Generator: Batch-generate test data from field templates — names, phone numbers, emails, dates, enums; one template line yields N JSON records. — https://dev.miaokit.tech/t/mock
- QR Code Generator: Turn text or links into QR codes with adjustable error correction, size and colors; rendered locally, downloadable as PNG. — https://dev.miaokit.tech/t/qrgen
- JSON to Type: Infer JSON structure locally and generate type definitions for TypeScript, Go, Java and 9 languages total — int/float and nullable fields included. — https://dev.miaokit.tech/t/json2type
- NanoID Generator: Generate NanoIDs locally in batches: 21 chars by default, URL-safe alphabet (A-Za-z0-9_-) by default — shorter than UUID, ideal as IDs. — https://dev.miaokit.tech/t/nanoid
- Placeholder Image Generator: Type width, height, label and colors to render an inline SVG placeholder in real time — copy the SVG source or Data URI for prototypes and mockups. — https://dev.miaokit.tech/t/placeholder
- UUID Parser: Break a UUID into version, variant and embedded timestamps — v1 carries MAC and time, v7 stores a millisecond timestamp in its first 48 bits; decode it locally with ease. — https://dev.miaokit.tech/t/uuidparse
- Password Strength Analyzer: Analyze your own password locally — estimate character space and entropy, flag common or repeated patterns and rough brute-force times; your input is never sent anywhere. — https://dev.miaokit.tech/t/pwdstrength
- Code to Image: Render syntax-highlighted code as a downloadable PNG — pick a theme and font size; ideal for share cards and docs, processed entirely locally. — https://dev.miaokit.tech/t/code2img

### DESIGN & MEDIA
- Color Toolkit: HEX / RGB / HSL conversion plus an auto-generated 10-step shade ramp (great for Tailwind palettes); one-click copy. — https://dev.miaokit.tech/t/color
- Image Compressor: Drop in a photo and compress it locally — WebP first with automatic JPEG fallback, adjustable quality; phone photos shrink to shareable sizes. — https://dev.miaokit.tech/t/img
- Image Converter: Convert between WebP, JPEG and PNG locally; PNG→JPG gets a white background, with automatic fallback when WebP is unsupported. — https://dev.miaokit.tech/t/imgconv
- Image to Base64: Two-way conversion between images and Base64 / Data URI — inline small icons or CSS backgrounds with one paste. — https://dev.miaokit.tech/t/imgb64
- Color Converter: Pure-math conversion across HEX / RGB / HSL / HSV / CMYK with input auto-detection — paste a color from your design file and go. — https://dev.miaokit.tech/t/colorcv
- Color Palette Generator: Derive harmonious palettes from a base color: complementary, analogous, triadic, split-complementary and monochrome — export CSS variables or Tailwind snippets. — https://dev.miaokit.tech/t/palette
- Contrast Checker: WCAG 2.x contrast calculation with AA / AAA pass-fail, both directions at once — stop guessing at accessible color pairs. — https://dev.miaokit.tech/t/wcag
- CSS Gradient Generator: Dial in linear / radial gradients with 2–3 color stops, drag angle and position sliders and copy the CSS directly. — https://dev.miaokit.tech/t/gradient
- Box Shadow Generator: Visually dial box-shadow — offset X/Y, blur, spread, color and inset, with multiple layers, live preview and one-click CSS copy. — https://dev.miaokit.tech/t/boxshadow
- Border Radius Generator: Visually tune border-radius with per-corner control in px or percentage — nail corners for cards, avatars and pill buttons in one place. — https://dev.miaokit.tech/t/radius
- Cubic Bezier Generator: Drag the control points to shape a cubic-bezier easing curve, preview the motion live with an animated box, and copy the CSS timing-function or JS values. — https://dev.miaokit.tech/t/bezier
- Color Name & Mixer: Map HEX / RGB values to and from common color names, and blend two colors by ratio into a new value — naming and mixing in one tool. — https://dev.miaokit.tech/t/colorname
- Image Cropper: Drag a crop region on a canvas with 1:1 / 4:3 / 16:9 presets and export PNG or JPEG locally — the image is never uploaded and the source stays intact. — https://dev.miaokit.tech/t/imagecrop
- Favicon Generator: Upload an image or type text / emoji to generate 16 / 32 / 48 / 180 / 512 favicons in one zip; canvas scaling and client-side zip, zero upload. — https://dev.miaokit.tech/t/favicon

### CODE FORMAT
- SQL Formatter: Beautify one-line SQL with uppercase keywords and indented clauses — a lifesaver when reviewing spaghetti queries. — https://dev.miaokit.tech/t/sql
- XML Formatter: Beautify or minify XML with tag-pair validation and error locating; declarations, comments and CDATA all handled. — https://dev.miaokit.tech/t/xml
- YAML Formatter: Validate and beautify YAML, convert to and from JSON without escaping CJK — verify K8s / CI configs as you edit. — https://dev.miaokit.tech/t/yaml
- TOML Formatter: Validate and beautify TOML, convert to and from JSON — a helper for Cargo, pyproject and other Rust/Python configs. — https://dev.miaokit.tech/t/toml
- Markdown Preview: Live Markdown preview with tables, code blocks and blockquotes; raw HTML is always escaped — paste safely. — https://dev.miaokit.tech/t/md
- JavaScript Minifier: Conservative JS minification: strips comments, indentation and blank lines while preserving strings and regexes verbatim — no renaming, still runs. — https://dev.miaokit.tech/t/jsmin
- CSS Formatter: Two-way CSS beautify and minify: one declaration per line, tidy nesting; minify keeps /*! comments and collapses zero units without reordering selectors. — https://dev.miaokit.tech/t/cssfmt
- HTML Formatter: Beautify or minify HTML: block elements on new lines, inline elements untouched; script/pre content preserved verbatim so rendering never changes. — https://dev.miaokit.tech/t/htmlfmt
- PX ⇄ REM Converter: Batch-convert between px and rem with an adjustable root font size — paste in design specs for responsive styles. — https://dev.miaokit.tech/t/pxrem
- JSON Minifier: Collapse formatted JSON into a single line in one click — strip newlines and indentation for smaller payloads and easier pasting into logs or URLs; precise error locating. — https://dev.miaokit.tech/t/jsonminify
- Tab / Spaces Converter: Convert between tabs and spaces in both directions with 2/4/8 width options — fix messy indentation from copied code in one click. — https://dev.miaokit.tech/t/tabspaces
- Line Ending Converter: Normalize line endings to CRLF / LF / CR with automatic detection and per-style counts — a lifesaver for cross-platform script errors. — https://dev.miaokit.tech/t/lineending
- TypeScript Type Stripper: Strip type annotations, interfaces and generics from TypeScript source to get runnable JavaScript — a conservative, lexer-based pass that leaves anything ambiguous untouched. — https://dev.miaokit.tech/t/ts2js
- HTML & SVG to JSX: Convert HTML / SVG snippets into React JSX — class→className, style strings to objects, self-closing tags and entities handled; perfect for pasting designer SVGs. — https://dev.miaokit.tech/t/html2jsx
- HTML to Markdown: Convert HTML to Markdown — keeps code blocks, tables, links, headings, lists, bold/italic and images; pure front-end DOMParser parsing with no heavy dependency. — https://dev.miaokit.tech/t/html2md

### UNIT CONVERT
- Unit Converter: Real-time conversion across length, weight, temperature, volume, area, time, data and speed — temperature offset handled correctly. — https://dev.miaokit.tech/t/convert
- Date & Time Zone Difference: See the gap between two dates in days, years and months at a glance (leap years and DST handled), plus wall-clock conversion across time zones. — https://dev.miaokit.tech/t/datediff
- Bandwidth & Data Rate Converter: Convert bit rates to byte rates (decimal 1000-based, with a strong Mb-vs-MB ×8 reminder) and estimate transfer time from file size and bandwidth. — https://dev.miaokit.tech/t/datarate
- Angle Converter: Convert between degrees, radians, gradians and turns in real time — handy for CSS rotate and canvas math. — https://dev.miaokit.tech/t/angle
- Chinese Numeral Converter: Convert numbers to Chinese uppercase/lowercase amounts with yuan/jiao/fen, negatives and decimals — zero merging and 整 suffix per accounting rules, ready for invoices. — https://dev.miaokit.tech/t/num2cn

### REFERENCE
- MIME Type Lookup: A quick extension ↔ MIME type lookup with live filtering by extension or media type — check Content-Type or upload validators in seconds. — https://dev.miaokit.tech/t/mime
- Emoji Search: Search a built-in emoji library by keyword or category in real time; click any emoji to copy it — perfect for posts and README badges. — https://dev.miaokit.tech/t/emoji
- HTTP Headers Reference: A reference of 60+ common request and response headers with usage, examples and security notes — filterable live by name, direction and category. — https://dev.miaokit.tech/t/httpheader
- Time Zone Reference: Browse IANA time zones with live current time and UTC offsets, searchable by name — handy for cron, log triage and cross-region meetings. — https://dev.miaokit.tech/t/tzlist
- Git Command Cheat Sheet: Scenario-based Git command cheat sheet — undo, revert, branching, rebase, stash, submodules — searchable and copy-ready. — https://dev.miaokit.tech/t/gitcheat

### FILE TOOLS
- File Metadata Reader: Drop or pick a local file to read metadata — name, size, type, last modified and more; read entirely on-device, nothing is uploaded. — https://dev.miaokit.tech/t/filemeta
- File Encoding Detector: Drop a text or file to detect its encoding locally — UTF-8 / UTF-16 / GBK with BOM awareness — and preview the content decoded with the detected encoding. — https://dev.miaokit.tech/t/encoding
- File ⇄ Base64: Convert any file to Base64 or a Data URI, and restore pasted Base64 back to a downloadable file — 20MB cap, fully local. — https://dev.miaokit.tech/t/fileb64
- File Type Identifier:  — https://dev.miaokit.tech/t/filesig

### DEV TOOLS
- URL Slug Generator: Turn titles or filenames into URL-friendly slugs: lowercase, spaces to dashes and special characters stripped — ready for routes and anchors. — https://dev.miaokit.tech/t/slugify
- curl to Code: Paste a curl command and get fetch / axios / Python requests / Go snippets — headers, data and url-encoding flags parsed automatically. — https://dev.miaokit.tech/t/curl2code
- Token Counter & Cost Estimator: Estimate LLM token usage and API cost locally — pick a model to see token count, input/output cost and context-window usage; nothing is uploaded. — https://dev.miaokit.tech/t/token
- Dotenv ⇄ JSON Converter: Parse .env files to JSON — quotes, comments, export prefixes and inline # all handled — and convert JSON back to .env with live key validation. — https://dev.miaokit.tech/t/dotenv
- chmod Calculator: Convert rwx notation to octal and back across owner/group/other, with setuid/setgid/sticky explained — directory and file scenarios included. — https://dev.miaokit.tech/t/chmod
- Semver Comparator: Compare and sort semver versions with prerelease/build metadata, and test ranges like ^ ~ >= — stop guessing dependency upgrades. — https://dev.miaokit.tech/t/semver
- IPv4 Subnet Calculator: Feed a CIDR to get network and broadcast addresses, usable host range and count, subnet mask, IP class and public/private scope; slice finer subnets by a new prefix. — https://dev.miaokit.tech/t/subnet
- OG & Meta Tag Generator: Fill in title, description, URL and image to generate complete Open Graph + Twitter Card + standard meta code, with live WeChat / Telegram / X card previews and JSON-LD. — https://dev.miaokit.tech/t/ogmeta
- Docker Run to Compose: Turn a docker run command into an equivalent docker-compose.yml — ports, volumes, environment, name, restart policy and network, all parsed locally with zero upload. — https://dev.miaokit.tech/t/docker
- Basic Auth Header: Encode user:password into an Authorization: Basic <base64> header with a copy-ready header and curl snippet; cross-linked with the HTTP Headers tool. — https://dev.miaokit.tech/t/basicauth