Free online developer tools that stay out of your way.

Live Mermaid editor for flowcharts, sequence, ER, class, state, gantt, and mindmaps.

Visual cloud architecture editor with AWS, GCP, and Azure component libraries.

Build sequence diagrams from actors and messages, then export Mermaid.

Model entities, fields, and relationships into Mermaid ER diagrams.

Generate box-and-arrow ASCII diagrams for docs and READMEs.

Beautify, minify, and validate JSON with one click.

Compare two JSON objects and visualize differences.

Convert between YAML and JSON for configs, K8s, and CI files.

Convert CSV tables to JSON arrays and back with delimiter detection.

Query JSON with path expressions like $.items[*].id.

Encode text to Base64 or decode Base64 back to text.

Percent-encode and decode URLs and query strings.

Escape and unescape HTML entities safely.

Format, minify, and check well-formed XML or HTML markup.

Convert numbers between binary, octal, decimal, and hex.

Pick colors and convert between HEX, RGB, and HSL.

Create QR codes from text or URLs and download as PNG.

Write Markdown with a live GitHub-flavored preview.

Test regular expressions with live match highlighting.

Compare two text blocks and highlight line differences.

Convert text between camelCase, snake_case, kebab-case, and more.

Store, organize, and share code snippets with tagging.

Decode and analyze JSON Web Tokens to view their contents.

Verify JWT signatures with HMAC secrets or RSA public keys.

Sign JWTs locally with HS256, HS384, or HS512 secrets.

Generate SHA-1, SHA-256, SHA-384, and SHA-512 hashes for text.

Compute HMAC digests and encrypt/decrypt with AES-GCM in the browser.

Generate UUID v1, v4, and v7 identifiers for your applications.

Generate strong passwords and secrets with configurable character sets.

Convert Unix timestamps to human-readable dates and back.

Paste a cron expression and see what it means in plain English.

Format and beautify SQL queries for readability.

Test REST APIs with requests, headers, environments, and responses.

Run GraphQL queries against any endpoint with variables and headers.

Parse cURL commands or OpenAPI ops into ready-to-send requests.

Map and transform JSON structures with an interactive flow diagram.