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Online tools can leave you guessing where sensitive data goes. Our local tools process on your device; network tools disclose their connections. Audit the MIT-licensed source to review how it works.

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API & Web Services

API Request Builder

Test HTTP and gRPC APIs, run request collections and start local mock servers

Open toolNetwork features · view data disclosure

GET/workspaces/playground

Example API response

{
  "workspace": "Playground",
  "status": "ready"
}

Your whole toolkit. One place.

147 tools. 15 categories. One place to get started.

Find a tool by name, task, format, or category.

API & Web Services13

API Request BuilderTest HTTP and gRPC APIs, run request collections and start local mock serversNetwork features · view data disclosure AsyncAPI ExplorerInspect AsyncAPI event contracts, channels, operations, servers, and messagesLocal processing Document Data ExplorerBrowse and query MongoDB, Firestore and Elasticsearch with encrypted saved connections and type-aware exportsNetwork features · view data disclosure

Artificial Intelligence6

A2A InspectorInspect Agent-to-Agent cards, check selected fields, exchange messages and view raw JSON-RPC 2.0 responsesNetwork features · view data disclosure Agent Card / MCP Manifest GeneratorBuild a valid A2A agent-card.json or MCP server config, then send it straight to the A2A or MCP inspector to testLocal processing Fine-Tuning Dataset ValidatorValidate JSONL fine-tuning datasets against OpenAI or Anthropic message schemas — entirely in your browserLocal processing

Certificates & Keys8

Certificate & CSR GeneratorGenerate self-signed X.509 certificates and Certificate Signing Requests (CSR) with RSA / ECDSA keysLocal processing Certificate Chain & SSLInspect live certificate chains through a disclosed server connection, or analyze pasted certificates locallyUses the mydevtools server Certificate InspectorDecode, fingerprint and convert X.509 certificates in PEM or DER; inspect live certificates from permitted public hosts.Network features · view data disclosure

Cryptography12

AES Encrypt & DecryptEncrypt and decrypt CryptoJS-compatible AES-CBC passphrase text locallyLocal processing BCrypt Hash & VerifyGenerate BCrypt hashes for passwords and verify passwords against existing hashesLocal processing Credential VaultEncrypt passwords, API keys, environment variables and saved connections locallyLocal processing

Data Converters11

CSV to JSON ConverterConvert CSV data to JSON arrays or objects with header detectionLocal processing CSV to XML ConverterConvert CSV data to XML format with customizable element namesLocal processing JSON / YAML / TOML / XML ConverterConvert in all twelve directions between JSON, YAML, TOML and XML with explicit mapping limitsLocal processing

Diff & Compare6

CSV DiffRow-keyed CSV comparison with column-level change highlighting — handles added, removed, and modified rowsLocal processing Image DiffPixel-perfect visual comparison: side-by-side, overlay, and difference modes with adjustable toleranceLocal processing JSON DiffCompare two JSON documents side by side with highlighted differencesLocal processing

Encoding & Decoding7

Base64 Encode / DecodeEncode and decode Base64 strings instantlyLocal processing Gzip Compress / DecompressCompress and decompress text using Gzip with Base64 encodingLocal processing Hex Encoder / DecoderEncode text to hexadecimal and decode hex strings back to text (UTF-8)Local processing

Formatters8

CSS FormatterBeautify and minify CSS stylesheets with vendor prefix handlingLocal processing HTML FormatterFormat, prettify and beautify HTML documents with customizable indentationLocal processing JavaScript FormatterBeautify and minify JavaScript code with configurable optionsLocal processing

Fun & Games7

Coin TossFlip a fair virtual coin with 3D animation — heads or tails with flip statisticsLocal processing Dice RollRoll polyhedral dice (d4–d20) with advantage/disadvantage mode for TTRPGs and probability experimentsLocal processing Magic 8-BallAsk a yes/no question and let the classic Magic 8-Ball reveal your fate with all 20 original responsesLocal processing

Generators14

.gitignore GeneratorCombine stack, editor and operating-system ignore patterns with custom overridesLocal processing Color Contrast CheckerCheck WCAG contrast ratios between foreground and background colorsLocal processing Credit Card GeneratorGenerate synthetic Luhn-valid card fixtures with security codes and expiry datesLocal processing

Image & Media7

Code ScreenshotCreate syntax-highlighted code images with themes, backgrounds, window controls and real PNG exportLocal processing Color Palette ExtractorExtract the dominant colours from any image — outputs HEX, RGB and HSL values ready to copyLocal processing Favicon, ICO & Maskable GeneratorGenerate PNG favicons, a six-size ICO, a safe-zone maskable icon and matching manifest in one ZIPLocal processing

Network11

CORS TesterTest requests from this browser origin, inspect exposed CORS headers and review possible causes of opaque failuresNetwork features · view data disclosure DNS LookupResolve A, AAAA, CNAME, MX, TXT, NS, SOA records for any hostname using public DNS-over-HTTPS resolversConnects directly from your browser Docker Compose AnalyzerReview Compose YAML services, ports, networks, volumes, and hygieneLocal processing

Reference6

HTTP Status Codes ReferenceSelected HTTP status codes with explanations, examples and primary sourcesLocal processing IP Ranges ReferenceReference guide for private, reserved, and special-use IP address rangesLocal processing MIME Types ReferenceComprehensive searchable database of MIME types (Content-Types) with file extensions, categories, and usage examples for web development, file uploads, and HTTP headersLocal processing

Text & Utilities22

Code SnippetsSave, search, format and copy project code snippets with syntax highlightingLocal processing Color Picker & ConverterPick colors and convert between HEX, RGB, HSL formatsLocal processing Cron Expression ParserParse, validate and explain cron expressions with next run timesLocal processing

Validators9

Credit Card ValidatorValidate and generate test credit card numbers with Luhn algorithmLocal processing Email ValidatorInspect email syntax and disposable-domain signalsConnects directly from your browser HTML ValidatorValidate HTML markup for errors and best practicesLocal processing

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More than a collection of tabs.

Keep the context. Get back to the work.

Give each project its own space.Keep notes, snippets, bookmarks and saved connections together. Switch projects when the work changes.Keep the next tool within reach.Open tools in parallel tabs in the workbench. Compare a response, check a query and pick up where you left off.Save the steps you repeat.Chain supported transformations into a saved workflow. Run the same sequence on the next input.

Know where your data goes.

Formatting, decoding and other local transformations run on your device. API and lookup tools contact the services shown in the tool when you run them. Native database and storage connections need the desktop app or local runtime.

Projects and preferences stay in this browser. Use the passphrase-protected vaults for credentials and private files, and export backups for safekeeping.