Free Online Web & Developer Tools
Web development requires navigating dozens of formats, protocols, and conventions simultaneously. This collection of professional-grade utilities covers the daily debugging and development workflow: formatting and diffing JSON payloads, decoding JWTs, parsing URLs, building cron schedules, computing Unix permissions, referencing HTTP status codes, and converting Docker commands. Every tool here is designed for speed — paste your data, get your answer, move on. No account, no file upload, no waiting for a server response.
Common Use Cases
22 Tools in This Category
In-Depth Guide: Free Online Web & Developer Tools
JSON in Modern Web Development
JSON has become the de facto language of the web. REST APIs, GraphQL responses, NoSQL databases, configuration files, package.json, .eslintrc, tsconfig.json — JSON is everywhere. Three tools in this category address different JSON workflow needs: **JSON Formatter** prettifies minified JSON with consistent indentation and syntax highlighting. It validates as you type, pinpointing exactly where a syntax error occurs. When debugging an API response, this is the first tool you reach for. **JSON Minifier** strips all whitespace from prettified JSON, reducing payload size by 20-30% for production API responses and reducing storage requirements in databases. **JSON Diff** compares two JSON objects and highlights what changed — additions (green), removals (red), and value changes (orange). Invaluable when debugging why a deployment changed API response shapes, or when reviewing schema migrations. **JSON Schema Generator** analyzes a sample JSON object and generates the corresponding JSON Schema — a specification that validates the structure. This is the starting point for OpenAPI/Swagger documentation and runtime validation with libraries like ajv.
JWT Tokens Explained
A JSON Web Token (JWT) is a compact, URL-safe string that encodes a set of "claims" about a subject — typically a user's identity and permissions. Defined by RFC 7519, JWTs are the standard authentication mechanism for stateless REST APIs and single-page applications. A JWT has three base64URL-encoded segments separated by dots: **Header** — The algorithm used to sign the token: `{"alg":"HS256","typ":"JWT"}` **Payload** — The claims (data): `{"sub":"user_123","exp":1705312200,"role":"admin"}`. Standard claims include: - `sub` — Subject (usually a user ID) - `exp` — Expiration time (Unix timestamp) - `iat` — Issued at time - `iss` — Issuer (your service name) - `aud` — Audience (intended recipient) **Signature** — HMAC or RSA signature that proves the token was not tampered with. The server validates this signature on every request. Our JWT Decoder reveals the header and payload instantly — perfect for debugging auth flows where you need to check if a token is expired, what permissions it grants, or what issuer created it.
Regular Expressions: Power and Pitfalls
Regular expressions (regex) are the most powerful text-processing tool available to developers — and one of the most misused. A well-crafted regex can replace hundreds of lines of conditional string logic. **When regex excels:** - Validating input formats (email, phone, date, credit card) - Extracting structured data from unstructured text (log parsing, web scraping) - Search-and-replace with capture groups in editors and build tools - Pattern matching in routing (URL path matching) **When regex is dangerous:** - Complex nested quantifiers can cause catastrophic backtracking (ReDoS vulnerability) - Maintaining complex patterns requires good documentation - Unicode handling requires careful flag configuration (/u flag in JavaScript) Our Regex Tester provides real-time match highlighting, capture group display, flag toggles, and match count — test before you ship.
Frequently Asked Questions
How do I decode a JWT token?
A JWT consists of three base64URL-encoded segments separated by dots. Use our JWT Decoder to paste any token and see the decoded header and payload instantly. Note: this only decodes — it does not verify the signature. Verification requires the signing key on the server.
What does "200 OK" vs "204 No Content" mean?
200 OK means the request succeeded and a response body is included. 204 No Content means the request succeeded but there is no body to return — common for DELETE requests and PUT updates that return no response body. See our HTTP Status Codes reference for all 60+ codes.
How do I convert a docker run command to docker-compose.yml?
Paste your docker run command into our Docker Run to Compose tool. It parses every flag (-p, -v, -e, --name, --network, etc.) and generates a valid docker-compose.yml service definition you can copy directly into your project.
What does chmod 755 mean in Unix?
755 means the owner has read+write+execute (7), while group and others have read+execute (5). This is the standard for web server executables and directories. Our chmod calculator lets you toggle permissions visually and shows both octal and symbolic notation.
What is a cron expression?
A cron expression is a five-field string (minute hour day-of-month month day-of-week) that defines a recurring schedule. "0 9 * * 1-5" means "9:00 AM, Monday to Friday." Our Cron Builder generates expressions visually with a plain-English explanation.