Developer Tools — JSON, Formatters, Regex, JWT, Subnets and More
Format JSON, code and SQL, turn JSON into YAML, CSV or typed code, test regular expressions, decode JWTs, read cron schedules and calculate subnets.
- JSON Formatter & Validator Paste JSON to pretty-print it, minify it, or find exactly where it is broken — with the line, column and a plain-language reason.
- JSON Compare See exactly what changed between two versions of a JSON config, API response or data file.
- Password Generator Create strong, random passwords with a cryptographically secure generator.
- UUID Generator Generate unique IDs in bulk — random UUID v4, time-sortable UUID v7 and ULID, or short Nano IDs — and inspect any UUID to read its version, variant and embedded timestamp.
- JWT Decoder Paste a JSON Web Token to see its header and payload, check whether it has expired, and verify the signature with a secret or public key.
- Regex Tester Write a regular expression, see every match highlighted as you type, inspect capture groups and try out replacements.
- Cron Expression Parser Paste a cron expression to see what it means in plain words and exactly when it will run next, in your time zone or the server's.
- JSON to YAML Converter Turn JSON into clean YAML for Kubernetes manifests, Docker Compose, CI pipelines and application config.
- YAML to JSON Converter Convert YAML config — Kubernetes manifests, Compose files, CI pipelines — into JSON for APIs and tools that only accept JSON.
- JSON to CSV Converter Turn a JSON array — an API response, a database export — into a CSV file that opens in Excel, Numbers or Google Sheets.
- CSV to JSON Converter Paste CSV exported from Excel, Google Sheets or a database and get a JSON array ready for an API or a script.
- Binary, Decimal & Hex Converter Enter a number in any base from 2 to 36 and see it in binary, octal, decimal, hexadecimal and a base of your choice at once.
- Color Converter & Contrast Checker Paste a color in any CSS format to get it as HEX, RGB, HSL, HSV, CMYK and OKLCH, check its contrast against a background for WCAG accessibility, and generate a matching light-to-dark shade scale.
- JavaScript Formatter Paste minified or messy JavaScript and get clean, consistently formatted code.
- CSS Formatter Turn minified or messy CSS into readable, consistently indented style sheets.
- HTML Formatter Make HTML readable again.
- XML Formatter Paste minified or single-line XML and get properly indented, readable output.
- SQL Formatter Turn long one-line queries into readable SQL with each clause and column on its own line.
- YAML Formatter Clean up YAML with consistent two-space indentation and spacing, and find syntax errors before they break a deployment.
- JavaScript Minifier Shrink JavaScript for production.
- CSS Minifier Compress style sheets for production.
- JSON to TypeScript Converter Turn a JSON sample — an API response, a config file, a fixture — into TypeScript interfaces you can paste into your code.
- JSON to Go Struct Converter Paste JSON and get Go struct definitions with json tags, ready for encoding/json.
- JSON to Pydantic Model Converter Paste JSON and get Pydantic models you can use to validate and parse data in Python.
- JSON to Rust Struct Converter Paste JSON and get Rust structs ready for serde_json.
- JSON to JSON Schema Generator Paste a JSON sample and get a JSON Schema describing it — types, nested objects, array items and which keys are required.
- IP Subnet (CIDR) Calculator Enter an address with a prefix like 192.168.1.10/24 to get everything about the network — addresses, masks, host range and size — for IPv4 and IPv6.
- Chmod Calculator Tick the read, write and execute boxes for owner, group and others to get the numeric and symbolic permission and the chmod command — or type 755 or rwxr-xr-x to see what it means.
- User Agent Parser Find out what your browser reports about itself, or decode a User-Agent string from server logs to see the browser, operating system and device behind a request — and spot search engine crawlers and scripts.
- HTTP Status Codes A complete, searchable list of HTTP response status codes.
- HTML to Markdown Converter Paste HTML source, or copy a section of any web page or document and paste it here, formatting and all.
- Excel to CSV Converter Open an .xlsx, .xls, .ods or Numbers file, choose a sheet and get CSV with the values exactly as they appear in Excel.
- Excel to JSON Converter Turn a spreadsheet into JSON you can use in code or an API.
- CSV to Excel Converter Paste CSV or open a .csv file and download a proper .xlsx workbook.
- JSON to Excel Converter Paste a JSON array, such as an API response, and download it as an .xlsx workbook.
- cURL to Code Converter Paste a curl command, for example one copied from your browser's developer tools, and get the same request as ready-to-run code.
- CSS Gradient Generator Build a gradient background by eye instead of by trial and error.
- XML to JSON Converter Turn an XML document, feed or API response into JSON you can use in JavaScript or any modern API.
- JSON to XML Converter Produce XML from JSON for older APIs, configuration files or SOAP-style integrations.
- JSON to TOML Converter Turn JSON into TOML for Rust's Cargo.toml, Python's pyproject.toml, Hugo and application config.
- TOML to JSON Converter Convert TOML config to JSON to process it in code or check the real structure of files like Cargo.toml and pyproject.toml.
- ULID Generator Generate ULIDs (Universally Unique Lexicographically Sortable Identifiers) in bulk for database keys, logs and message IDs, or paste a ULID to see when it was created.
- Nano ID Generator Generate Nano IDs, random IDs that are shorter than UUIDs and safe to put in a URL — handy for short links, file names, component keys and database keys.
- SSH Key Generator Generate an SSH key pair in your browser for server logins or GitHub and GitLab deploy keys.
- JSONPath Tester Type a JSONPath expression to pull data out of JSON and see the matching values, and the full path of each match, as you type.
- docker run to Docker Compose Paste one or more docker run commands to get the equivalent compose.yaml.
- Docker Compose to docker run Paste a compose.yaml or docker-compose.yml to get an equivalent docker run command for every service — handy for starting a container on a machine without Compose, or for checking exactly how a service is started.
- Mermaid Live Editor Draw flowcharts, sequence diagrams, Gantt charts and more from a few lines of text.
- Nginx Config Generator Enter your domain, pick the kind of site and tick the features you need to get a ready-to-use nginx server configuration.
- SQL Playground Write SQL without installing a database.
- Run JavaScript Online Paste or write JavaScript and click Run to see console.log, warn and error output — for trying snippets, practising algorithms or debugging a bit of logic.
- Color Contrast Checker Enter a text colour and a background colour to get the WCAG contrast ratio and see whether normal and large text meet AA and AAA.
- HTML, CSS and JavaScript Playground Write HTML, CSS and JavaScript on the left and watch the result update on the right, with a console below showing console.log output and script errors.
- Common Regex Patterns Ready-to-use regular expressions for everyday validation — email, URL, domain, IPv4 and MAC addresses, integers, decimals and money amounts, dates and times, usernames, strong passwords, hex colors, UUIDs and semantic versions, plus Chinese phone, ID and postcode formats.
- SLA & Uptime Calculator 99.9% availability allows about 43 minutes of downtime a month; 99.99% only about 4.
- RAID Calculator Before building a NAS or server array, see how much space four 8 TB disks give you in RAID 5 versus RAID 6 and how many can fail.
- Unzip Online Got a RAR or 7z file on your phone and nothing to open it with?
- Merge and Split Excel Files Collecting reports from every team into one sheet, or breaking a master list up by department, are two of the most tedious Excel chores.
- VLSM Calculator Planning an office network, a homelab or a networking exam?
- systemd Service File Generator Keep a Node.js, Python or Go program running on a Linux server, start it at boot and restart it when it crashes — without remembering every systemd option.
- Firewall Rule Generator Open the ports your server needs and close the rest without looking up three different syntaxes.