# GitCircle > Browser-based developer tools that load instantly. No signup. Whenever possible, your data stays on your device. Catalog: 136+ tools at https://gitcircle.com. Prefer client-side processing so payloads stay on-device when possible. GitCircle is a static developer utility site. Pages are HTML; tool logic runs in the browser. Use the links below for canonical free tools (JSON, JWT, Base64, regex, Git, AI prompts, MCP, diffs, and more). ## What GitCircle does GitCircle provides browser-based tools for: - Formatting and validating JSON, YAML, XML, SQL, and Markdown. - Encoding and decoding Base64, URLs, HTML, and Unicode. - Inspecting and generating JWTs, hashes, UUIDs, and passwords. - Testing and explaining regular expressions. - Generating Git and GitHub configuration. - Converting cURL requests into code. - Comparing JSON, text, YAML, SQL, and other data. - Working with OpenAPI and API payloads. - Building AI/LLM prompts, schemas, token estimates, and model payloads. - Inspecting and generating MCP tools, schemas, JSON-RPC messages, and server configurations. ## Best for GitCircle is best for: - Quick format, validate, convert, and inspect jobs without creating an account. - Keeping secrets, tokens, prompts, and payloads on-device while debugging. - JWT, hash, UUID, password, and regex checks during local development. - Git/GitHub, Docker, cron, cURL, and env-file helpers in one place. - Side-by-side diffs of JSON, text, YAML, SQL, Markdown, XML, URLs, and env files. - AI/LLM prompt, schema, token, cost, and model-payload prep work. - MCP tool schemas, JSON-RPC messages, and client server configs. ## Privacy model - Default: tool logic runs in the browser. For browser-only tools, input is not uploaded to GitCircle servers. - Favorites and recently used tools are stored in this browser localStorage only; that list is not uploaded. - Google Analytics (GA4) may record which tool was opened or run, not the contents of browser-only tool input. - If a tool needs the network, it is marked runsInBrowser: false and will not claim that data stays local. - Full policy: https://gitcircle.com/privacy ## Start here - [Home](https://gitcircle.com): Fast, free tools for developers. - [All tools](https://gitcircle.com/tools): Searchable directory of every browser tool. - [Categories](https://gitcircle.com/categories): Browse by craft: JSON, encoding, Git, AI, MCP, Diff, and more. - [About](https://gitcircle.com/about): Product promises: instant load, no account, privacy-first when possible. ## Popular tools - [JSON Formatter](https://gitcircle.com/tools/json-formatter): Format and beautify JSON online for free. - [JSON Validator](https://gitcircle.com/tools/json-validator): Check whether a payload is valid JSON. - [JWT Decoder](https://gitcircle.com/tools/jwt-decoder): Decode a JWT header and payload without verifying. - [Base64 Encoder](https://gitcircle.com/tools/base64-encoder): Encode text as Base64. - [Regex Tester](https://gitcircle.com/tools/regex-tester): Run a regular expression against a string. - [UUID Generator](https://gitcircle.com/tools/uuid-generator): Generate RFC 4122 version 4 UUIDs. - [Unix Timestamp Converter](https://gitcircle.com/tools/unix-timestamp-converter): Convert unix time, millis, or date strings. - [URL Encoder](https://gitcircle.com/tools/url-encoder): Percent-encode text for URLs. - [SHA-256 Hash](https://gitcircle.com/tools/sha-256-hash): SHA-256 digest for security payloads. - [Password Generator](https://gitcircle.com/tools/password-generator): Generate a random password in your browser. - [SQL Formatter](https://gitcircle.com/tools/sql-formatter): Indent SQL and uppercase keywords. - [JSON Diff](https://gitcircle.com/tools/json-diff): Compare two JSON documents with path-level changes and a formatted line diff. ## AI & LLM tools - [AI Markdown Formatter](https://gitcircle.com/tools/ai-markdown-formatter): Normalize Markdown headings and lists for LLM-friendly documents. - [AI Response Diff](https://gitcircle.com/tools/ai-response-diff): Compare two model responses line by line. - [Anthropic Message Formatter](https://gitcircle.com/tools/anthropic-message-formatter): Format prompts into an Anthropic Messages API payload. - [JSON -> Prompt](https://gitcircle.com/tools/json-to-prompt): Turn JSON context into a readable user prompt with fenced blocks. - [JSON Schema -> TypeScript](https://gitcircle.com/tools/json-schema-to-typescript): Generate TypeScript types from a JSON Schema object. - [JSON Schema -> Zod](https://gitcircle.com/tools/json-schema-to-zod): Generate Zod schemas from JSON Schema for runtime validation. - [LLM Context Window Calculator](https://gitcircle.com/tools/llm-context-window-calculator): See how much context budget remains for common models. - [LLM JSON Validator](https://gitcircle.com/tools/llm-json-validator): Validate JSON from model output, including ```json fences. - [OpenAI Message Formatter](https://gitcircle.com/tools/openai-message-formatter): Format plain or tagged text into an OpenAI chat payload. - [OpenAPI -> LLM Tool Schema](https://gitcircle.com/tools/openapi-to-llm-tool-schema): Convert OpenAPI operations into OpenAI function/tool definitions. - [Prompt -> JSON](https://gitcircle.com/tools/prompt-to-json): Parse role-tagged prompts or headings into structured JSON. - [Prompt Diff](https://gitcircle.com/tools/prompt-diff): Compare two prompts before you send them to a model. - [Prompt Formatter](https://gitcircle.com/tools/prompt-formatter): Normalize spacing and paragraph breaks in LLM prompts. - [Prompt Token Counter](https://gitcircle.com/tools/prompt-token-counter): Estimate token count for a prompt without sending it to an API. - [Structured Output Schema Generator](https://gitcircle.com/tools/structured-output-schema-generator): Infer a strict JSON Schema for structured LLM outputs. - [System Prompt Builder](https://gitcircle.com/tools/system-prompt-builder): Build a system prompt from JSON fields or a one-line goal. - [Token/Cost Calculator](https://gitcircle.com/tools/token-cost-calculator): Estimate USD cost from input and output token counts. ## MCP tools - [MCP Inspector](https://gitcircle.com/tools/mcp-inspector): Inspect an MCP tool definition - name, description, input schema, and parameter types. - [MCP JSON-RPC Tester](https://gitcircle.com/tools/mcp-json-rpc-tester): Validate and pretty-print JSON-RPC 2.0 messages used by MCP. - [MCP Server Config Generator](https://gitcircle.com/tools/mcp-server-config-generator): Generate MCP server configuration snippets for Cursor, Claude Desktop, and other clients. - [MCP Tool Schema Generator](https://gitcircle.com/tools/mcp-tool-schema-generator): Build an MCP tool definition with name, description, and typed parameters. ## Everyday essentials - [YAML -> JSON](https://gitcircle.com/tools/yaml-to-json): Convert YAML into JSON. - [cURL Generator](https://gitcircle.com/tools/curl-generator): Build a curl command from JSON. - [Cron Expression Explainer](https://gitcircle.com/tools/cron-expression-explainer): Explain a 5-field cron expression. - [.gitignore Generator](https://gitcircle.com/tools/gitignore-generator): Build a .gitignore from stack names. - [JSON Schema -> TypeScript](https://gitcircle.com/tools/json-schema-to-typescript): Generate TypeScript types from a JSON Schema object. - [JSON Schema -> Zod](https://gitcircle.com/tools/json-schema-to-zod): Generate Zod schemas from JSON Schema for runtime validation. - [Prompt Token Counter](https://gitcircle.com/tools/prompt-token-counter): Estimate token count for a prompt without sending it to an API. - [MCP Server Config Generator](https://gitcircle.com/tools/mcp-server-config-generator): Generate MCP server configuration snippets for Cursor, Claude Desktop, and other clients. ## Categories - [JSON & Data](https://gitcircle.com/categories/json): Format, validate, convert, and inspect structured data. - [Encoding & Text](https://gitcircle.com/categories/encoding): Encode, decode, hash, and transform text. - [IDs & Random Data](https://gitcircle.com/categories/ids): Generate UUIDs, passwords, and random strings. - [JWT & Security](https://gitcircle.com/categories/security): Inspect tokens, hashes, and security-related payloads. - [Git & GitHub](https://gitcircle.com/categories/git): Helpers for commits, ignores, diffs, and GitHub workflows. - [Regex](https://gitcircle.com/categories/regex): Test, explain, and escape regular expressions. - [Date & Time](https://gitcircle.com/categories/datetime): Timestamps, timezones, cron, and date math. - [SQL & Database](https://gitcircle.com/categories/sql): Format SQL and convert between queries and data. - [Web & API](https://gitcircle.com/categories/api): HTTP, cURL, URLs, and API payloads. - [Docker & DevOps](https://gitcircle.com/categories/devops): Compose files, env files, and cluster YAML helpers. - [AI](https://gitcircle.com/categories/ai): AI-assisted developer tools. Serverless later, never client API keys. - [MCP](https://gitcircle.com/categories/mcp): Inspect, validate, and generate Model Context Protocol configs and schemas. - [Diff](https://gitcircle.com/categories/diff): Compare JSON, text, YAML, SQL, URLs, and other formats side by side. ## Optional - [Full tool catalog](https://gitcircle.com/llms-full.txt): Every tool with privacy, layout, and related tools. - [Machine-readable catalog](https://gitcircle.com/tools.json): JSON catalog of every tool, related slugs, and metadata. - [Sitemap](https://gitcircle.com/sitemap-index.xml): Machine-readable list of all indexable URLs. - [Privacy](https://gitcircle.com/privacy): How GitCircle handles data for browser tools. - [Terms](https://gitcircle.com/terms): Terms of use. - [Contact](https://gitcircle.com/contact): Reach the maintainer.