Free Developer Tools — Format, Encode, Decode & Convert
A focused toolbox for everyday development work: format and validate JSON, encode and decode Base64 and URLs, decode and verify JWTs, test regular expressions, generate hashes and UUIDs, convert timestamps, and calculate subnets — plus a full set of MCP and AI-agent tools for building and securing Model Context Protocol servers.
Every tool here runs entirely in your browser. That's not just a speed benefit — it means API responses, tokens, secrets, MCP configs and customer data you paste in are never transmitted anywhere. No signup, no rate limits, no waiting on a server round-trip.
{ } JSON11
JSON Formatter & Validator
Pretty-print, minify and validate JSON with exact error line & column.
JSON Tree Viewer
Explore JSON as a collapsible tree.
JSON Diff / Compare
Compare two JSON documents and see what changed.
JSON to TypeScript
Generate TypeScript interfaces from JSON.
JSON ↔ CSV Converter
Convert JSON to CSV and CSV back to JSON.
JSON ↔ YAML Converter
Convert JSON to YAML and YAML back to JSON.
JSON ↔ XML Converter
Convert JSON to XML and XML back to JSON.
JSON Schema Generator
Generate a draft-07 JSON Schema from a sample.
JSONPath Tester
Query JSON with JSONPath expressions.
JSON Repair
Fix broken JSON — quotes, trailing commas, comments.
JSON Escape / Unescape
Escape text into a JSON string, or unescape it back.
64 Base644
Base64 Encode/Decode
Encode & decode Base64 with URL-safe, MIME and live modes.
File to Base64
Convert any file to Base64 or a data URI — in your browser.
Base64 to File
Decode Base64 (or a data URI) back into a downloadable file.
Image to Base64
Convert an image to a Base64 data URI with preview + CSS/HTML.
🔗 URL4
URL Encode/Decode
Percent-encode/decode with the right scope, live — plus double-encoding detection.
URL Parser
Break a URL into host, path, query params & hash.
Query String Builder
Build & edit query strings from key/value pairs.
Slugify — URL Slug Generator
Turn a title into a clean, SEO-friendly URL slug.
🤖 MCP & Agents18
MCP Security Scanner
Scan an MCP server config for prompt-injection, exfiltration & tool poisoning.
MCP Config Generator
Generate a valid MCP server config for Claude, Cursor, VS Code & Windsurf.
MCP Config Validator
Validate an mcp.json / claude_desktop_config.json and catch common mistakes.
Prompt Secret Redactor
Mask API keys, tokens & PII in a prompt before you send it to an LLM.
Prompt Injection Checker
Scan untrusted text for prompt-injection patterns before feeding it to an agent.
Tool Definition Generator
Generate a tool/function-calling schema for MCP, Anthropic (Claude) & OpenAI.
MCP tools/list Inspector
Inspect & validate an MCP tools/list response — params, required fields & schema issues.
System Prompt Linter
Review a system prompt for role clarity, guardrails & prompt-injection resistance.
Tool Definition Converter
Convert a tool/function schema between MCP, Anthropic (Claude) & OpenAI formats.
MCP Config Merger
Merge multiple MCP server configs into one file — deduped, with conflicts flagged.
Prompt Template Manager
Fill {{variables}} in a reusable prompt with a live preview and missing-value checks.
WebMCP Tool Generator
Generate WebMCP tool definitions — declarative HTML & imperative JS — to make your site agent-ready.
WebMCP Readiness Checker
Check your page HTML for WebMCP tools and get agent-readiness fixes — is your site WebMCP-ready?
Deep Agent Scaffold Generator
Design a deep agent (planning, subagents, tools) → get runnable LangChain deepagents code + a diagram.
LLM Red-Team Prompt Generator
Generate adversarial test prompts to red-team your own AI agent — mapped to the OWASP LLM Top 10.
OWASP LLM Top 10 Assessment
Self-assess your LLM app against the OWASP LLM Top 10 — get a risk score and mitigations.
JSON Schema to Zod / Pydantic / TypeScript
Convert a JSON Schema to Zod, a Pydantic model or a TypeScript interface for typed LLM tools & APIs.
Context Window / Token Budget Planner
Plan a prompt's token budget against a model's context window — system, RAG, history, output & cost.
🔑 JWT3
More Developer tools
Regex Tester
Test regular expressions with live match highlighting.
Hash Generator
Generate SHA-1/256/384/512 hashes of text.
UUID Generator
Generate v4 UUIDs, single or in bulk.
Timestamp Converter
Convert between Unix epoch and human dates.
Case Converter
camelCase, snake_case, kebab-case, Title Case, and more.
Mermaid Viewer & Editor
Render Mermaid diagrams live — flowcharts, sequence, class & more — and export SVG or PNG.
CIDR / Subnet Calculator
Compute network, broadcast, mask, and host range.
What's included
- JSON — formatter and validator, tree viewer, diff, repair, schema generator, JSONPath tester, and converters to TypeScript, CSV, YAML and XML.
- JWT — decoder, encoder/signer and signature verifier using the Web Crypto API.
- Base64 — text, file, image and data-URI encoding and decoding.
- URL — percent encoder/decoder, URL parser, query-string builder and slug generator.
- Utilities — regex tester, hash generator, UUID generator, timestamp converter, case converter and CIDR calculator.
- MCP & Agents — MCP config generator and validator, security scanner, tools/list inspector, tool-definition (schema) generator, system-prompt linter, secret redactor and injection checker for people building with AI agents.
Why local processing matters for developers
Debugging usually means pasting real data — a production API response, an auth token, a config file. Pasting those into a tool that posts them to someone else's server is a quiet security problem, and one that's easy to overlook under time pressure. Because these tools compute in the browser, the data stays in the tab you're working in. You can use them on internal payloads without a second thought, and they keep working offline once the page has loaded.
Frequently asked questions
Is my data sent to a server?
No. Every developer tool here runs in your browser using JavaScript and the Web Crypto API, so what you paste never leaves your machine.
Can I use these on production data?
That's exactly the point of processing locally — nothing is transmitted or logged. As a general habit, still avoid pasting live production secrets into any web page, ours included.
Do the tools work offline?
Once a tool page has loaded, the processing itself needs no network connection, so it keeps working if you go offline.
Is there any rate limit or signup?
Neither. There's no account, no quota and no throttling, because there's no server doing the work.