Free Developer Tools
The small things you reach for mid-task — decode a token, work out a cron, turn a payload into Java. No sign-up, no limits.
Every tool runs in your browser — nothing you paste is uploadedFormat & inspectBeautify, validate and inspect your data
- JSON Formatter — Format, validate, minify and explore JSON with a collapsible tree.
- SQL Formatter — Pretty-print and tidy SQL with keyword casing options.
- JWT Decoder — Decode header and payload, check expiry, verify HMAC signatures.
- Regex Tester — Test patterns live with match highlighting and capture groups.
- JSON Diff — Compare two documents by path, ignoring key order.
- Difference Checker — Compare two blocks of text and see every added, removed and changed line.
ConvertMove between common formats
- JSON → Java POJO — Turn any JSON into Java classes with getters, setters and Jackson.
- JSON → Record — Turn any JSON into immutable Java 17+ records, nested types and all.
- YAML ↔ JSON — Convert either way, with quoting that preserves types.
- Properties ↔ YAML — Spring application.properties to application.yml and back.
- Base64 Encode/Decode — Standard or URL-safe, with UTF-8 handled properly.
- OpenAPI → Java DTO — Turn an OpenAPI 3 spec into Java records or classes with Jackson.
- OpenAPI → Spring — Generate Spring Boot controllers from a spec, one per tag.
- OpenAPI → Postman — Convert a spec into an importable Postman v2.1 collection.
Generate & measureProduce values and size things up
- UUID Generator — Random v4 or time-ordered v7, in bulk, with the Java to match.
- Cron Generator — Build cron expressions, read them in English, preview next runs.
- Timestamp Converter — Epoch to date and back, across time zones, with Java snippets.
- HTTP Request Builder — Build a request and get curl, HttpClient, RestTemplate and WebClient code.
- Kafka Message Tester — Compose a record, see its partition, headers and producer code.
- Kafka Message Size — Real on-the-wire record and batch size, against broker limits.
Why these run in your browser
Most online tools of this kind post what you paste to a server. That is a poor trade for a developer: the things you most want to decode — a production JWT, an API payload, a connection string in a SQL snippet — are exactly the things that should not be sent to a stranger's backend.
Everything here is JavaScript running on your machine. There is no upload, no account, no history kept, and each tool keeps working with the network disconnected. The exceptions are clearly marked: the HTTP builder generates request code, it does not send the request, and the difference checker compares in the browser but has two opt-in buttons that do send text.
Most used: JSON formatter, difference checker, JSON diff, JWT decoder and SQL formatter.