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Developer tools that never leave your browser

Format, encode, decode, generate — plus the everyday utilities for building with LLMs. Fast, keyboard-friendly and open source. Every byte is processed locally; no API key, no upload.

AI · Structured output & data New

{S} JSON Schema Generator Generate a JSON Schema from sample JSON. Strict mode makes it valid for OpenAI structured outputs, and one click wraps it as an OpenAI response_format, OpenAI function or Anthropic tool definition. Zod JSON to Zod Convert sample JSON into a Zod schema plus its inferred TypeScript type. Ready for validating API responses and LLM structured outputs with the Vercel AI SDK or OpenAI SDK. JL JSONL Validator Validate JSON Lines files line by line, preview records in a table, and check OpenAI-style chat fine-tuning data (roles, missing assistant replies, empty content). Convert JSONL ⇄ JSON arrays. FIX JSON Repair Fix invalid JSON instantly: strips markdown fences and chatty text, adds missing quotes and commas, removes trailing commas and comments, converts Python True/None, and closes JSON that was cut off mid-stream. ⇄ Chat Format Converter Convert conversation histories between the OpenAI Chat Completions, Anthropic Messages and Gemini request formats — including system prompts, images, tool calls and tool results. API OpenAPI to LLM Tools Convert an OpenAPI 3 or Swagger 2 spec (JSON or YAML) into tool definitions for OpenAI function calling, Anthropic Claude tool use or MCP servers. $refs are resolved and each endpoint becomes one tool. ✓{} JSON Schema Validator Validate JSON data against a JSON Schema (draft-07, 2019-09, 2020-12) and see every error with its path. Paste an OpenAI response_format or a Claude tool definition directly — the schema is extracted automatically. cos Vector Similarity Calculator Paste two embedding vectors and get cosine similarity, cosine distance, angle, dot product, Euclidean and Manhattan distance. Accepts raw arrays or full embedding API responses.

AI · Prompts & integration New

TOK LLM Token Counter Count tokens exactly with OpenAI’s o200k_base (GPT-4o, GPT-4.1, GPT-5, o-series) and cl100k_base (GPT-4, GPT-3.5) tokenizers, and see how your text is split. Runs offline in your browser. MD AI Markdown Cleaner Paste an answer from ChatGPT, Claude, Gemini or DeepSeek and remove the **, ##, backticks and citation markers. Get clean plain text, or copy as formatted rich text for Word, Google Docs, email and Feishu. MCP MCP Config Generator Fill in an MCP server once and get the correct config for Claude Desktop, Claude Code, Cursor, VS Code and Windsurf — local (stdio) or remote (HTTP) servers, with env vars and headers. SSE LLM Stream (SSE) Parser Paste a raw streaming response (Server-Sent Events or NDJSON) from OpenAI, Anthropic Claude, Google Gemini, Ollama or any OpenAI-compatible API, and get the final text, reasoning, tool calls and token usage. {{}} Prompt Template Filler Paste a prompt template with {{variables}}, {placeholders} or ${vars}. A form is generated for each variable, the filled prompt previews live with its token count, and you can export ready-to-use Python or JavaScript code. RAG RAG Text Chunker Preview how a document is split into chunks for embeddings and RAG. Recursive splitting by paragraphs, lines and sentences (Chinese punctuation included), chunk size in tokens or characters, overlap, and JSON export. llms llms.txt Generator Create an llms.txt file for your website or docs: a Markdown index that tells LLMs and AI agents which pages matter. Import links from your sitemap.xml and download the result. $/M LLM API Cost Calculator Estimate per-request, daily and monthly API cost across OpenAI, Anthropic, Google and DeepSeek models. Accounts for prompt caching, long-context price tiers and context-window limits. API LLM API Playground Send requests to OpenAI, Anthropic, DeepSeek, OpenRouter, Ollama or any OpenAI-compatible API with your own key. Watch streaming output, time to first token, usage, tool calls and structured output — and copy the request as curl.

Format & Convert

{ } JSON Formatter Format, validate and minify JSON instantly. Pinpoints syntax errors by line and column, sorts keys, and runs entirely in your browser. TS JSON to TypeScript Convert JSON into TypeScript interfaces or type aliases. Infers nested objects, arrays, optional fields and union types — locally in your browser. RGB Color Converter Convert colors between HEX, RGB, HSL and OKLCH with a live preview and WCAG contrast check against black and white text. curl curl to Code Convert curl commands into JavaScript fetch, Python requests or Go net/http code. Handles headers, JSON bodies, form data, basic auth and multi-line commands copied from API docs or DevTools. SQL SQL Formatter Format and beautify SQL queries for MySQL, PostgreSQL, SQLite, SQL Server, BigQuery, Snowflake and more. Choose keyword case and indentation — locally in your browser. YML YAML ⇄ JSON Convert YAML to JSON and JSON to YAML instantly, with clear error messages. Handy for Kubernetes manifests, GitHub Actions, Docker Compose and OpenAPI specs. CSV CSV ⇄ JSON Convert CSV to JSON and JSON to CSV in your browser. Detects commas, semicolons and tabs, handles quoted fields and line breaks, infers numbers and booleans, and flattens nested JSON into dot-notation columns. Py JSON to Pydantic / Go / Rust Generate Pydantic models, Go structs with json tags, or Rust serde structs from sample JSON. Detects integers vs floats, optional and nullable fields, and renames keys that aren’t valid identifiers. $.. JSONPath Tester Run JSONPath expressions against your JSON and see matching values or their exact paths. Supports wildcards, recursive descent, slices, unions and filter expressions like [?(@.price < 10)]. {±} JSON Diff Compare two JSON documents by structure, not by text. Lists every added, removed and changed field with its path, ignores key order, and can optionally ignore array order.

Encode & Decode

B64 Base64 Encode / Decode Encode text to Base64 or decode Base64 back to text. Full UTF-8 support (emoji, Chinese), URL-safe variant, and file to Base64 conversion. %20 URL Encode / Decode Percent-encode or decode URLs and query parameters, and break any URL into its parts and query string — in your browser. JWT JWT Decoder Decode a JSON Web Token to see its header, payload and claims. Shows expiry status and readable dates for exp, iat and nbf. Tokens never leave your browser. 0x Number Base Converter Convert numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36 — with arbitrary precision, digit grouping and two’s-complement view. \u HTML Entity & Unicode Escape Encode and decode HTML entities, convert text to and from Unicode escapes (\uXXXX, \u{…}, Python, CSS), escape JSON strings, and inspect hidden characters such as zero-width spaces.

Images

IMG Image Compressor Compress and resize images in your browser. Convert to WebP or JPEG, adjust quality, set a maximum width or height, and batch-process many files — nothing is uploaded. b64 Image to Base64 Convert an image to a Base64 data URI and copy it as HTML, CSS, Markdown or a ready-made Claude API image block — or decode Base64 back into a downloadable image.

Text & Regex

.* Regex Tester Test JavaScript regular expressions with live match highlighting, capture groups, named groups and replace preview. DIFF Text Diff Compare two texts or code snippets and highlight the differences by line, word or character. Ideal for comparing prompt versions, AI rewrites, config files and JSON. M↓ Markdown Editor Write Markdown with a live GitHub-flavoured preview: tables, task lists, code blocks. Copy the rendered HTML or rich text, download a .md file, and see word count and reading time. aA Case Converter Convert identifiers between camelCase, PascalCase, snake_case, CONSTANT_CASE, kebab-case, Title Case and more. Handles acronyms like XMLHttpRequest and converts many lines at once. 字 Word Counter Count words, characters (with and without spaces), Chinese/Japanese/Korean characters, sentences, paragraphs, reading time and LLM tokens as you type. Handles mixed-language text correctly.

Generators & Utilities

ID UUID Generator Generate random UUID v4 or time-ordered UUID v7 in bulk using cryptographically secure randomness. Uppercase and no-hyphen options. # Hash Generator Calculate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of text or files. Uses the Web Crypto API and runs fully offline in your browser. *** Password & API Key Generator Generate strong random passwords and secret tokens (hex, base64url, base62) with the Web Crypto API. Shows entropy in bits, excludes look-alike characters on request, and never sends anything over the network. QR QR Code Generator Create QR codes for URLs, text, Wi-Fi networks and contact details. Choose size, colors and error correction, then download a PNG or a crisp SVG. Generated locally; codes never expire. 755 Chmod Calculator Tick read/write/execute boxes or type 755, rwxr-xr-x or u+x,go-w, and get the matching octal, symbolic notation and ready-to-copy chmod commands. Supports setuid, setgid and sticky bits. /24 IP Subnet (CIDR) Calculator Calculate network and broadcast addresses, usable host range, subnet mask and wildcard for any IPv4 CIDR block. Check whether an IP is in a subnet, split networks and convert IP ranges to CIDR. UA User-Agent Parser Parse any User-Agent string into browser, rendering engine, operating system and device type. Identifies search engines and AI crawlers such as GPTBot, ClaudeBot and PerplexityBot, and generates a robots.txt to block them. Abc Fake Data & Lorem Ipsum Generator Generate realistic fake records — names, emails, phones, addresses, companies, dates, UUIDs — in English or Chinese, as JSON, JSONL, CSV or SQL INSERT. Also generates Lorem ipsum and Chinese placeholder text.

Date & Time

UTC Unix Timestamp Converter Convert Unix timestamps (seconds or milliseconds) to human-readable dates in local time, UTC and ISO 8601, and convert dates back to timestamps. */5 Cron Expression Parser Explain a cron expression in plain English or Chinese and list its next run times in your time zone. Supports ranges, steps, lists, month and weekday names, and @daily-style macros.

Developer reference

200 404 502 HTTP status codes Every HTTP status code explained, with causes and fixes.

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Building in Public
· 2 min read

Why Every Tool on codes.im Runs in Your Browser

Developers paste tokens, logs and customer data into online tools every day. The reasoning behind “your data never leaves the browser”, how it’s built, and what it costs.

#build-in-public#privacy#astro