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The full toolbox.

45 free developer tools, grouped by what they do. Every one runs entirely in your browser, so nothing you paste is uploaded.

AI

Everything for building with large language models: prompts, tokens, agents, cost, and context.

Prompting7

prompt linterNew

Catch vague, conflicting, or unclear prompts.

prompt diffNew

Compare two prompts and see what changed.

prompt simulatorNew

See what a vague prompt forces AI to guess.

prompt builderNew

Answer 6 questions, get a clear prompt.

prompt optimizerNew

Score, fix & restructure any prompt, all-in-one.

good vs bad promptsNew

Before/after prompt rewrites, with the why.

prompt x-rayNew

See the structure of a prompt.

Models & cost6

token counterNew

Count tokens with the real OpenAI tokenizers.

context window viz

See what fills a model's context budget.

context budget analyzerNew

Find which files eat your context window.

llm vram calculatorNew

Estimate VRAM to run a model locally.

llm cost calculatorNew

Estimate API cost from token usage.

ai profit calculatorNew

Price, users & usage in. Margin & break-even out.

Agents & MCP6

ai pattern explorer

Compare agent design patterns side by side.

mcp config generatorNew

Build & validate an MCP server config.

mcp inspectorNew

Audit an MCP config: errors, secrets, broad access.

agent memory simulatorNew

See how AI memory keeps or loses facts.

ai pattern builderNew

Compose an agent flow, export scaffolding.

tool call visualizerNew

Step through the function-calling loop.

Build & ship8

structured output builder

Schemas for OpenAI, Anthropic, Gemini & JSON Schema.

rag chunking visualizerNew

See how a document splits into RAG chunks.

ai stack explainerNew

What building blocks an AI product uses.

embedding explorerNew

Real embeddings + semantic search, in-browser.

claim & citation checkerNew

Flag unsupported claims to verify.

scope sorterNew

MoSCoW your roadmap, find the MVP.

launch readiness rubricNew

Score your own idea across 6 dimensions.

ai architecture generatorNew

Describe an app, get an architecture (BYO key).

JSON

Generate types and convert JSON, the data format behind most APIs and schemas.

json → typescript

Paste JSON, get a typed TS interface.

json → go

Generate Go structs from any JSON payload.

Encoding

Encode, decode, and inspect Base64 and JWTs, the tokens behind authentication.

jwt decoder

Decode & inspect JSON Web Tokens.

base64 encode/decode

Encode or decode Base64, incl. URL-safe.

Converters

Convert between data formats like CSV, YAML, and JSON, and turn cURL commands into code.

csv ⇄ json

Convert tabular data both ways, instantly.

.htaccess gen

Redirects & rewrite rules, the easy way.

curl → code

Turn a cURL command into fetch, axios, or Python.

yaml ⇄ json

Swap between YAML and JSON cleanly.

Text

Format and clean up text and code, from messy SQL to naming conventions.

sql formatter

Beautify and standardize messy SQL.

case converter

camelCase, snake_case, kebab, PascalCase.

Time & Cron

Build and read cron schedules for recurring jobs, in plain English.

cron generator

Build & read crontab expressions, in plain English.

Feeds

Validate, preview, and convert RSS and Atom feeds, the open web’s syndication format.

rss validator

Check any feed against the spec.

opml converter

Import, view & convert OPML subscription lists.

rss to json

Turn any RSS or Atom feed into clean JSON.

feed preview

Read any feed as a clean, human-friendly list.

Email

Check a domain’s email deliverability: SPF, DKIM, and DMARC.

deliverability checkerNew

Check a domain's SPF, DKIM & DMARC, with a score & fix.

Network

Look up DNS records and WHOIS data for any domain.

dns lookupNew

See any domain's A, MX, TXT, NS & more, live.

whois lookupNew

Registrar, dates, status & nameservers via RDAP.

token counterNew

Count tokens with the real OpenAI tokenizers.

context window viz

See what fills a model's context budget.

context budget analyzerNew

Find which files eat your context window.

structured output builder

Schemas for OpenAI, Anthropic, Gemini & JSON Schema.

ai pattern explorer

Compare agent design patterns side by side.

rag chunking visualizerNew

See how a document splits into RAG chunks.

mcp config generatorNew

Build & validate an MCP server config.

mcp inspectorNew

Audit an MCP config: errors, secrets, broad access.

prompt linterNew

Catch vague, conflicting, or unclear prompts.

prompt diffNew

Compare two prompts and see what changed.

prompt simulatorNew

See what a vague prompt forces AI to guess.

prompt builderNew

Answer 6 questions, get a clear prompt.

prompt optimizerNew

Score, fix & restructure any prompt, all-in-one.

good vs bad promptsNew

Before/after prompt rewrites, with the why.

llm vram calculatorNew

Estimate VRAM to run a model locally.

llm cost calculatorNew

Estimate API cost from token usage.

ai profit calculatorNew

Price, users & usage in. Margin & break-even out.

agent memory simulatorNew

See how AI memory keeps or loses facts.

ai pattern builderNew

Compose an agent flow, export scaffolding.

ai stack explainerNew

What building blocks an AI product uses.

tool call visualizerNew

Step through the function-calling loop.

prompt x-rayNew

See the structure of a prompt.

embedding explorerNew

Real embeddings + semantic search, in-browser.

claim & citation checkerNew

Flag unsupported claims to verify.

scope sorterNew

MoSCoW your roadmap, find the MVP.

launch readiness rubricNew

Score your own idea across 6 dimensions.

ai architecture generatorNew

Describe an app, get an architecture (BYO key).

json → typescript

Paste JSON, get a typed TS interface.

JSON

json → go

Generate Go structs from any JSON payload.

JSON

jwt decoder

Decode & inspect JSON Web Tokens.

Encoding

base64 encode/decode

Encode or decode Base64, incl. URL-safe.

Encoding

csv ⇄ json

Convert tabular data both ways, instantly.

Converters

.htaccess gen

Redirects & rewrite rules, the easy way.

Converters

curl → code

Turn a cURL command into fetch, axios, or Python.

Converters

yaml ⇄ json

Swap between YAML and JSON cleanly.

Converters

sql formatter

Beautify and standardize messy SQL.

Text

case converter

camelCase, snake_case, kebab, PascalCase.

Text

cron generator

Build & read crontab expressions, in plain English.

Time & Cron

rss validator

Check any feed against the spec.

Feeds

opml converter

Import, view & convert OPML subscription lists.

Feeds

rss to json

Turn any RSS or Atom feed into clean JSON.

Feeds

feed preview

Read any feed as a clean, human-friendly list.

Feeds

deliverability checkerNew

Check a domain's SPF, DKIM & DMARC, with a score & fix.

dns lookupNew

See any domain's A, MX, TXT, NS & more, live.

Network

whois lookupNew

Registrar, dates, status & nameservers via RDAP.

Network