All developer tools
60 tools, grouped by what you are working on. Every one runs client-side — your input is never uploaded.
AI
Count tokens, estimate model cost, clean up prompts and generate tool-calling schemas before you spend money on an API call.
Prompt CleanerFind and remove the smart quotes, zero-width characters and hidden Unicode that a copy-paste puts into an AI prompt — and see exactly what was in there.Prompt Token CounterCount the tokens in a prompt exactly, in your browser, with a real BPE tokenizer — then see the cost across GPT, Claude and Llama models before you send it.LLM Cost CalculatorPrice a real workload across GPT and Claude models — requests per day, tokens in and out, and the prompt cache hit rate that usually decides the bill.Context Window CalculatorSee where a model's context window actually goes — prompt, tools, history, attachments and the reply's own space — and exactly what to cut when it overflows.Prompt Diff ViewerCompare two versions of a prompt word by word, and see what the edit costs — token delta, monthly bill, and the share of the total it accounts for.Prompt OptimizerTighten a prompt with named, reversible rules, then see the token and cost saving. Deterministic — no model call, nothing rewritten silently.JSON to Prompt GeneratorTurn a JSON sample into a structured prompt template — typed field list, worked example and a JSON Schema, all derived from one document.Function Calling GeneratorPaste a TypeScript or Python function signature and get the tool-use schema for OpenAI, Anthropic and Gemini. Unreadable types are reported, never guessed.OpenAI Structured Output Schema BuilderCheck a JSON Schema against the structured-outputs strict subset, or build one from a sample response. Finds why the API returns a 400.AI Output FormatterRecover usable JSON from a model's reply — strips fences, repairs trailing commas and smart quotes, and lists every repair it made.AI Temperature & Top-p SimulatorWatch temperature, top-p, top-k and min-p reshape a token distribution, with the arithmetic shown at each stage. Paste your own logprobs, or start from the sample.
JSON
Format, validate, compare and convert JSON. Everything runs in your browser — payloads never leave your machine.
JSON Formatter & ValidatorFormat, validate and minify JSON in your browser. Pinpoints syntax errors by line and column, sorts keys for clean diffs, and never uploads your data.JSON MinifierStrip whitespace from JSON and see the exact byte savings. Parses before minifying, so invalid input is located rather than mangled.JSON to TypeScriptGenerate TypeScript interfaces from a JSON sample, merging every record so differing keys become optional and varying types become unions.JSON Diff & CompareCompare two JSON documents structurally, so reformatting and key order are ignored and only real changes are reported — with a JSON Patch export.JSON Schema ValidatorValidate JSON against a JSON Schema (draft 2020-12) and get every failure located by JSON Pointer, with unsupported keywords listed rather than skipped.JSON to CSV & CSV to JSON ConverterConvert JSON to CSV and CSV to JSON in either direction, with RFC 4180 quoting, delimiter detection, nested-object flattening and type inference you control.JSONPath TesterRun a JSONPath expression against a document and see every matching node with its normalized path — filters, wildcards and recursive descent included.JSON to Zod SchemaGenerate a Zod schema from a JSON sample, with string formats and integers inferred only when every sample agrees. Zod 4 and 3 output.
SQL
Format, beautify and minify SQL, and turn queries into something a reviewer can read.
SQL FormatterFormat and beautify SQL for PostgreSQL, MySQL and SQL Server — clauses on their own lines, subqueries indented, literals untouched.SQL MinifierCollapse a SQL query to one line and strip comments, without touching string literals, quoted identifiers or the meaning of the query.SQL Query BuilderBuild a parameterised SELECT, INSERT, UPDATE or DELETE for Postgres, MySQL or SQL Server — with a warning when the query is valid but not what you meant.SQL Query ExplainerRead a SQL query clause by clause and see what it actually does — including the outer join your WHERE clause quietly turned into an inner one.
API
Convert cURL commands into real code and inspect HTTP headers without leaving the browser.
cURL to JavaScript Fetch ConverterPaste a cURL command and get clean fetch() code with headers, body, auth and method preserved. Nothing is sent to a server.cURL to Python Requests ConverterTurn a cURL command into idiomatic Python `requests` code — headers, JSON bodies, form data, basic auth and query strings included.cURL to Axios ConverterConvert a cURL command to Axios request code — config object, headers, JSON or form body and basic auth mapped automatically. Runs entirely in your browser.cURL to Node.js ConverterConvert a cURL command to Node.js code using only the built-in https module — no dependency to install, Content-Length and status checks handled for you.GraphQL FormatterFormat or minify a GraphQL query, mutation, fragment or SDL schema with a real parser — syntax errors show the exact line and column, nothing invented.HAR File AnalyzerOpen a HAR file and see the network waterfall, timing breakdown and findings — plus a one-click redacted copy safe to send, since HAR files leak tokens.HTTP Header AnalyzerPaste response headers from curl or DevTools and get them explained, with missing security headers, CSP weaknesses, cookie flags and cache contradictions flagged.
OpenAPI
Validate specs, diff versions and generate clients from an OpenAPI document.
OpenAPI ValidatorValidate an OpenAPI 3.0 or 3.1 document and get every structural error located by JSON Pointer, with unresolved references reported rather than skipped.Swagger & OpenAPI FormatterConvert an OpenAPI or Swagger file between YAML and JSON, sort its paths and schemas, and put every key back into specification order.OpenAPI Diff CheckerCompare two OpenAPI versions and see which changes actually break existing clients, with the reason for every verdict spelled out.OpenAPI TypeScript Client GeneratorTurn an OpenAPI 3 document into a typed TypeScript fetch client with no dependencies — and see exactly which parts the spec left too vague to type.OpenAPI Mock Server GeneratorGenerate example responses from an OpenAPI spec and export a mock you run locally — MSW handlers, an Express server or plain fixtures. Reproducible from a seed.
Regex
Test, explain and build regular expressions with live match highlighting.
Regex TesterTest JavaScript regular expressions against sample text with live match highlighting, named capture groups and a replace preview — all six flags explained.Glob Pattern TesterTest glob and .gitignore patterns against a list of paths and see exactly which rule matched each one — including which negation won.Regex GeneratorBuild a regex from labelled blocks, or infer one from examples that should and should not match — verified against both sets before you're asked to trust it.Regex Cheat SheetEvery token, quantifier, class, group and lookaround on one searchable page — each with a live example you can run, and the flavour differences called out.
Security
Decode JWTs, encode Base64 and generate credentials locally. Nothing is transmitted or logged.
JWT DecoderDecode a JWT's header and payload, check expiry, and verify HS256/384/512 signatures — entirely client-side, and decoding is never confused with verifying.Base64 Encoder & DecoderEncode and decode Base64 and Base64URL with full Unicode support, plus file-to-data-URI conversion for images. Runs offline — nothing is ever uploaded.Hash GeneratorGenerate SHA-1, SHA-256, SHA-384, SHA-512 and HMAC digests of text or a file, in hex or Base64 — computed locally with WebCrypto.Password GeneratorGenerate strong random passwords and passphrases with a computed entropy readout — unbiased, cryptographically random, never transmitted.JWT GeneratorSign a JWT with HS256, HS384 or HS512 and custom claims, generate a strong signing secret, and see which claims a validator will object to.SSL Certificate DecoderDecode a PEM X.509 SSL certificate to read its subject, issuer, SANs, key size and expiry date — parsed in your browser, never uploaded.
DevOps
Validate Docker Compose and Kubernetes manifests, and tidy up YAML and .env files.
ENV ParserConvert a .env file to JSON, YAML, shell exports, Docker flags or tfvars, and catch duplicate keys and quoting mistakes before they reach a container.YAML to JSON ConverterConvert YAML to JSON and JSON to YAML, reformat a config file, and get a line number for the indentation mistake instead of a stack trace.Cron Expression ParserExplain a cron expression in plain English and list the next times it will actually run, in UTC or your own timezone — step values and weekday ranges included.Docker Compose ValidatorValidate a Docker Compose file and catch the mistakes that only fail at `up` — a depends_on with no target, an undeclared volume, two services on one port.Kubernetes YAML ValidatorValidate Kubernetes manifests locally and catch what the API server only hints at — bad selectors, memory in millibytes, a removed apiVersion.
Database
Generate identifiers, format schemas and build queries.
UUID GeneratorGenerate cryptographically random UUID v4 and time-sortable UUID v7 in bulk, then copy them as a list, JSON array or SQL insert.Prisma Schema FormatterFormat a Prisma schema the way prisma format does — fields aligned into columns — and catch duplicate fields and models with no identifier.Mock Data GeneratorGenerate realistic seed rows from a one-line-per-field schema and export them as JSON, CSV, NDJSON or SQL inserts. Seeded, so the output is reproducible.ULID GeneratorGenerate lexicographically sortable ULIDs with real monotonic ordering, read the timestamp back out of one, and convert between ULID and UUID.Mongo Query BuilderBuild MongoDB find filters and aggregation pipelines visually, and get them as mongosh, Node driver or PyMongo code — with OR runs always grouped explicitly.
Utilities
Timestamps, URL encoding, QR codes, Markdown preview — the small things you look up constantly.
URL Encoder & DecoderPercent-encode and decode URLs and query strings, with explicit component, full-URL and form modes. Runs entirely in your browser.Unix Timestamp ConverterConvert epoch seconds, milliseconds, microseconds and nanoseconds to a date in any timezone and back, with BigInt precision so nanosecond values are never rounded.Text Diff CheckerCompare two blocks of text with line and word-level highlighting, whitespace and case options, and a unified diff you can save as a patch.Markdown to HTML Converter & PreviewConvert Markdown to HTML with a live preview, copy the markup, or save it as a PDF — raw HTML is escaped, so a pasted document cannot run anything.QR Code GeneratorGenerate a QR code from any text or URL and download it as SVG or PNG. Encoded entirely in your browser — the data never reaches a server, unlike most QR sites.