Free Online Developer Tools

Format JSON and code, inspect HTML and schemas, and build reviewed configuration drafts with free online developer tools.

Choose the right tool

Choose a formatter to improve readability, a validator to check declared syntax or schema, and a decoder to inspect encoded values. A decoder does not authenticate a token, and formatted code is not automatically safe to execute.

Available tools

• JSON Formatter and Validator

  Validate JSON syntax, format with two or four spaces, or minify it for copying and downloading. Works with pasted JSON in your browser.

• SQL IN List Builder

  Convert a list of lines into a SQL IN (...) fragment. Quote text safely for the fragment, preserve leading zeros or select numeric values.

• CSV to JSON and JSON to CSV Converter

  Convert CSV tables to JSON arrays or JSON arrays of objects to CSV. Supports comma, semicolon and tab delimiters, quotes and multiline cells.

• Unix Timestamp Converter

  Convert Unix seconds or milliseconds to ISO dates and readable time zones. Convert ISO dates back to Unix timestamps.

• UUID v4 Generator

  Generate one or up to 1000 random UUID v4 identifiers in your browser. Copy the list or download the values as a text file.

• URL Encoder and Decoder

  Encode or decode URL text. Choose component mode for parameter values or full URL mode to preserve URL separators.

• Base64 Encoder and Decoder

  Encode UTF-8 text to standard Base64 or decode Base64 back to text. Supports Unicode and emoji with copy and download controls.

• Markdown Editor & Preview

  Preview sanitized Markdown locally.

• Markdown to HTML

  Convert Markdown to sanitized HTML.

• HTML to Markdown

  Convert HTML structure to Markdown without executing the source.

• HTML Formatter

  Indent HTML using a syntax-aware formatter.

• HTML Minifier

  Minify HTML while preserving meaningful text and inline spacing.

• CSS Formatter

  Parse and pretty-print CSS rules.

• CSS Minifier

  Parse CSS and generate compact syntax.

• JavaScript Formatter

  Format JavaScript without executing it.

• JavaScript Minifier

  Minify JavaScript with compression and mangling disabled.

• SQL Formatter

  Format SQL queries online with readable indentation and uppercase keywords.

• XML Formatter & Validator

  Validate XML syntax and format element-only documents. Mixed content is preserved.

• XML ↔ JSON Converter

  Convert XML to a lossless node-tree JSON format or reconstruct XML.

• JSON ↔ YAML Converter

  Convert between JSON data and YAML with bounded alias expansion.

• YAML Formatter & Validator

  Parse and reformat YAML. Comments are preserved.

• JSON Tree Viewer

  Explore JSON in an expandable tree.

• JSONPath Tester

  Evaluate JSONPath selectors. Script evaluation is disabled.

• JSON Unescape and Escape

  Unescape a quoted JSON string into readable text, or escape plain text for use as a JSON string.

• HTML Entity Encoder / Decoder

  Encode HTML special characters or decode entities.

• Regular Expression Tester

  List regex matches and capture groups in a worker with a time limit.

• JWT Decoder

  Decode a JWT header and payload. This does not verify its signature.

• Hash Generator

  Create SHA-256, SHA-384 or SHA-512 hashes from UTF-8 text.

• HMAC Generator

  Generate a keyed HMAC with a UTF-8 secret.

• Number Base Converter

  Convert arbitrary-size integers between bases 2 through 36.

• Text ↔ Binary Converter

  Convert UTF-8 text and space-separated 8-bit binary bytes.

• String to Hex Converter

  Convert strings to space-separated UTF-8 hexadecimal bytes, or decode compact and whitespace-separated hex back to text.

• JSON Comparison

  Compare JSON values by structure and report changed paths, ignoring formatting.

• Cron Expression Explainer

  Explain Unix or common Spring cron schedules and show the next runs in a selected time zone.

• JSON to Java Classes

  Generate Java classes or records from JSON examples; optionally include Lombok and Jackson annotations.

• JSON to TypeScript Interfaces

  Generate TypeScript interfaces from JSON examples, including nested values and array unions.

• JSON Schema Validator

  Validate JSON against a supplied draft-07 schema and report field errors locally.

• SQL Parameter Substitution

  Substitute positional SQL placeholders for debugging; skip quoted text and comments.

• PostgreSQL Query Plan Viewer

  Inspect pasted PostgreSQL EXPLAIN JSON, expand the plan tree and compare estimates with actual rows.

• Log Analyzer

  Count log levels, list error lines and sort recognized elapsed-time entries.

• File Checksum Calculator

  Calculate a SHA file checksum and compare it with an expected hash.

• URL Query Editor

  Inspect, replace, append or remove query parameters while preserving the URL fragment.

• Color Contrast Checker

  Calculate WCAG contrast ratios for two opaque sRGB colors and report text thresholds.

• Unicode Code Point Inspector

  List Unicode code points, UTF-16 units and UTF-8 bytes for each character.

• XPath Tester

  Evaluate browser XPath 1.0 expressions against local XML.

• Remove XML Comments

  Remove XML comment nodes while preserving element and text content.

• Extract XML Attributes

  List XML element paths, attribute names and values as JSON.

• Flatten JSON with Paths

  Convert JSON to typed JSON Pointer entries, including container records.

• Rebuild Flattened JSON

  Rebuild JSON from typed JSON Pointer entries produced by Flatten JSON with Paths.

• List JSON Paths

  List JSON Pointer paths to every property and array item.

• Sort JSON Object Keys

  Sort object keys recursively using lexical ordering; preserve array order.

• Merge JSON Objects

  Deep-merge two JSON objects with configurable scalar conflict handling.

• Remove JSON Fields

  Remove selected object properties using exact JSON Pointer paths.

• Filter JSON Array

  Keep array objects whose selected top-level field matches a scalar JSON value.

• Group JSON Array

  Group objects by a scalar top-level field, retaining each group and its count.

• Sort JSON Array by Field

  Sort array objects by a string or numeric top-level field; missing values sort last.

• NDJSON and JSON Converter

  Convert newline-delimited JSON records to a JSON array or convert an array to NDJSON.

• Java String Literal Encoder

  Encode text as one Java string literal with escaped control characters.

• SQL String Literal Encoder

  Encode one string as an ANSI/PostgreSQL standard SQL literal; reject backslash ambiguity.

• POSIX Shell Argument Quoter

  Quote text as one literal POSIX-shell argument without executing commands.

• Dotenv to JSON

  Parse a simple single-line .env file into string-valued JSON; no variable expansion.

• HTTP Header Parser

  Parse pasted HTTP headers and preserve repeated header values.

• Semantic Version Comparator

  Compare strict SemVer 2.0.0 versions; ignore build metadata.

• UUID Inspector

  Inspect UUID format, version bits and variant; read the timestamp of version 7 UUIDs.

• Base64URL Encoder and Decoder

  Encode UTF-8 text as URL-safe Base64 or strictly decode Base64URL text.

• Rename JSON Object Keys

  Rename top-level properties using an explicit JSON name map.

• Remove Null JSON Properties

  Recursively omit null object properties while keeping array positions.

• Remove Null Array Entries

  Remove null entries from one JSON array.

• JSON Array Deduplicator

  Keep the first occurrence of each serialized JSON array value.

• JSON Structure Statistics

  Count node types and maximum nesting depth.

• JSON Primitive Value Extractor

  Collect primitive leaf values from a JSON structure.

• JSON Object to Entry Pairs

  Convert top-level object properties into key/value pairs.

• Entry Pairs to JSON Object

  Build an object from unique string-keyed entry pairs.

• JSON Object to Parallel Arrays

  Separate object keys and values into aligned arrays.

• Parallel Arrays to JSON Object

  Pair a unique string-key array with a same-length value array.

• JSON Array Slice

  Extract an index range from a JSON array.

• JSON Array Chunker

  Split an array into consecutive fixed-size groups.

• Flatten Nested JSON Arrays

  Flatten arrays to a selected depth without flattening object properties.

• Transpose JSON Matrix

  Swap rows and columns of a rectangular JSON matrix.

• Reverse JSON Array

  Reverse the top-level array while retaining value types.

• Rotate JSON Array

  Move leading array entries to the end.

• JSON Array Intersection

  Return unique serialized values present in both arrays.

• JSON Array Set Difference

  Keep unique first-array values absent from a second array.

• JSON Array Set Union

  Combine JSON arrays and keep first serialized occurrences.

• JSON Array Cartesian Product

  Generate every pair from two JSON arrays.

• JSON Array Numeric Aggregator

  Report sum, mean and extrema for a strictly numeric JSON array.

• JSON Record Position Finder

  Locate the first matching record and return its zero-based position.

• Index JSON Records by Key

  Create a keyed object from records with unique non-empty string keys.

• Keyed JSON Object to Records

  Move object keys into a new field on each record.

• Boolean Text to JSON

  Convert a disclosed set of boolean tokens into a JSON array.

• Lines to JSON String Array

  Encode each input line as a JSON string, preserving content.

• JSON String Array to Lines

  Join a JSON array of strings as text lines.

• JSON Number Stringifier

  Recursively convert numeric JSON values into decimal strings.

• Trim JSON String Values

  Recursively trim string values without renaming object keys.

• JSON Non-ASCII Escaper

  Serialize JSON with non-ASCII UTF-16 units written as Unicode escapes.

• NDJSON Line Validator

  Validate each non-empty line independently and report syntax errors.

• JSON Leaf Path Report

  Report leaf values with their escaped JSON Pointer paths.

• JSON Key Case Converter

  Convert object keys recursively to camelCase or snake_case.

• JSON Type Outline

  Describe observed JSON value types without claiming a full schema.

• Zip JSON Arrays

  Pair corresponding JSON array entries; reject unequal lengths.

• Partition JSON Records

  Separate records by an exact scalar top-level field match.

• JSON Merge Patch Applier

  Apply RFC 7396-style object merge patches with null deletion.

• JSON Depth Pruner

  Replace containers beyond a chosen nesting depth with a marker.

• JSON Record Field Coverage

  Report how many records contain each top-level field.

• IPv4 Integer Converter

  Convert an IPv4 address to its unsigned 32-bit decimal value.

• Integer to IPv4 Converter

  Convert an unsigned 32-bit decimal integer to dotted IPv4.

• IPv4 Subnet Calculator

  Calculate network, broadcast, mask and address count from IPv4 CIDR.

• IPv4 Range Size Calculator

  Count addresses in an inclusive IPv4 address interval.

• IPv4 Binary Representation

  Display each IPv4 octet as eight binary bits.

• IPv4 CIDR Membership Checker

  Check whether an IPv4 address is inside a CIDR network.

• IPv6 Address Expander

  Expand a compressed IPv6 address to eight four-digit groups.

• IPv6 Address Compressor

  Compress the longest leftmost run of two or more zero groups.

• URL Component Inspector

  Inspect an HTTP URL’s origin, hostname, path, query and fragment.

• Remove URL Credentials

  Remove embedded usernames and passwords from an HTTP URL.

• URL Fragment Remover

  Remove a URL fragment while preserving query parameters.

• Relative URL Resolver

  Resolve a relative reference against an absolute HTTP base URL.

• Same-Origin URL Checker

  Compare scheme, host and effective port of two HTTP URLs.

• Tracking Parameter Remover

  Remove common UTM and click-tracking query parameters.

• Canonical Query Sorter

  Sort query parameter names stably while preserving repeated-value order.

• URL Hostname List Extractor

  Validate URL lines and extract distinct normalized hostnames.

• UTF-8 Byte Inspector

  Report encoded byte positions, decimal bytes and hexadecimal bytes.

• Hex Byte List to Decimal

  Convert hexadecimal byte pairs to decimal byte values.

• Decimal Byte List to Hex

  Convert a decimal list of bytes from 0–255 into hexadecimal pairs.

• Adler-32 Checksum Calculator

  Calculate the Adler-32 checksum of UTF-8 encoded text.

• CRC-32 Checksum Calculator

  Calculate the standard reflected CRC-32/ISO-HDLC checksum of UTF-8 text.

• Base32 Text Encoder

  Encode UTF-8 text with the RFC 4648 Base32 alphabet and padding.

• Base32 Text Decoder

  Decode canonical padded or unpadded Base32 into strict UTF-8 text.

• Percent-Encoded Byte Inspector

  Inspect percent byte escapes without treating plus signs as spaces.

• Data URI Inspector

  Inspect a data URI’s media type, parameters and encoding.

• PEM Block Formatter

  Wrap valid Base64 in labeled PEM-style delimiters and 64-character lines.

• PEM Block Inspector

  Extract PEM labels and Base64 payload byte counts without executing content.

• Email Address Component Inspector

  Inspect one simple ASCII mailbox address and its domain labels.

• JSON Nested Object Collector

  Collect every object container with its JSON path.

• JSON Nested Array Collector

  Collect array containers and their paths, including nested arrays.

• JSON Property Type Filter

  Keep top-level properties whose JSON value type matches the selection.

• JSON Sensitive Key Redactor

  Replace values for explicitly named keys at every object depth.

• JSON Numeric String Parser

  Convert canonical decimal strings to finite numbers while retaining zero-prefixed IDs.

• JSON Blank String to Null

  Convert empty or whitespace-only JSON string values to null.

• JSON String Value Replacer

  Replace literal text inside JSON string values without changing keys.

• JSON Nested Array Limiter

  Trim every array container to its first N entries.

• JSON Array Enumerator

  Wrap array values with their original zero-based indices.

• JSON Array Sliding Windows

  Create overlapping array windows using a window length and step.

• JSON Array Run-Length Encoder

  Combine consecutive structurally serialized equal values into count records.

• JSON Run-Length Array Expander

  Expand value/count records into an array with a 10,000-item bound.

• Consecutive JSON Record Grouper

  Group only consecutive records sharing the same selected field.

• JSON Record Deduplicator by Field

  Keep the first or last record for each serialized key-field value.

• JSON Record Field Coalescer

  Append a field from the first non-null value among chosen source fields.

• JSON Record Default Filler

  Fill missing top-level record fields from an explicit default object.

• JSON Numeric Record Field Statistics

  Calculate finite numeric statistics for one required record field.

• JSON Nested Array Exploder

  Create one record per element of a selected top-level array field.

• JSON Pointer Resolver

  Resolve an RFC 6901 JSON Pointer with escaped slash and tilde tokens.

• JSON Pointer Value Editor

  Replace or delete one existing JSON Pointer target.

• JSON Patch Difference Generator

  Generate add/remove/replace operations to transform one JSON value into another.

• JSON Patch Subset Applier

  Apply add, remove, replace and test JSON Patch operations.

• JSON Sample to Schema Draft

  Generate a conservative JSON Schema draft from an observed sample.

• Simple JSON Schema Example Generator

  Build a deterministic example for a documented basic JSON Schema subset.

• Deterministic JSON Serializer

  Sort object keys recursively and serialize compactly for reproducible comparison.

• JSON Record Field Order Normalizer

  Reorder record fields using a supplied priority list, retaining all other fields.

• JSON Record Field Cross-Tab

  Count combinations of two selected JSON record fields.

• JSON Record Key Join

  Join two record arrays on one scalar key while retaining left/right namespaces.

• JSON Parent-Child Record Nesting

  Build a bounded tree from unique id and parent references.

• Numeric Array to Matrix Reshaper

  Reshape a flat JSON numeric array into equal-width rows.

• HTML Anchor Inventory

  Extract anchor destinations, text, targets and relationship attributes.

• Empty HTML Link Text Checker

  Find anchors with neither text nor an accessible label.

• New-Tab Link Relationship Checker

  Inspect links opening new tabs for explicit noopener/noreferrer tokens.

• HTML Image Alt Attribute Audit

  Report missing, empty and non-empty image alternative text.

• HTML Image Source Inventory

  Collect src and srcset attributes from image and source elements.

• HTML Heading Hierarchy Report

  Report heading levels and upward jumps larger than one level.

• HTML Form Field Inventory

  List form controls with names, types, values and required flags.

• HTML Form Label Association Checker

  Inspect whether form controls have explicit labels or ARIA label references.

• HTML Table to JSON Records

  Read the first simple HTML table using its first row as unique field names.

• HTML Data Attribute Extractor

  Collect data-* attribute values from each matching element.

• HTML ARIA Attribute Inventory

  Collect role and aria-* declarations for manual accessibility review.

• Duplicate HTML ID Finder

  Report repeated non-empty id attribute values in a fragment.

• HTML CSS Class Inventory

  Count each class token used by HTML elements.

• HTML Embedded Style Collector

  Collect style element text and inline style attribute declarations.

• HTML Inline Event Handler Finder

  Find event-handler attributes for manual code review.

• HTML Button Label Report

  List buttons, explicit types, labels and disabled states.

• HTML Semantic Landmark Inventory

  Count semantic regions and explicit ARIA roles in an HTML fragment.

• HTML Table Caption and Header Audit

  Report captions, header-cell counts and merged-cell use for each table.

• CSS Custom Property Inventory

  Extract simple custom property declarations and var() references.

• CSS Color Token Extractor

  Collect hexadecimal and common functional CSS color tokens.

• CSS Numeric Unit Inventory

  Count dimension-unit tokens used in CSS source.

• CSS Important Declaration Finder

  Locate !important annotations with line numbers.

• CSS Font Stack Extractor

  Collect declared font-family values from CSS source.

• CSS URL Reference Extractor

  Extract quoted or unquoted url() resource references.

• CSS Comment Remover

  Remove block comments while preserving quoted CSS string contents.

• XML Sitemap Generator

  Generate a bounded URL sitemap from absolute HTTP(S) URL lines.

• Robots.txt Rule Generator

  Build one user-agent group with explicit disallow paths and optional sitemap.

• Web App Manifest Builder

  Create a basic web app manifest from explicit branding fields.

• Organization JSON-LD Builder

  Format user-supplied organization identity as JSON-LD.

• UTC Calendar Event ICS Builder

  Generate an RFC-style calendar event using explicit UTC times and an identifier.

• SQL SELECT Statement Builder

  Generate a quoted SELECT statement with a separate positional parameter array.

• Safe cURL GET Command Builder

  Generate a shell-quoted cURL GET command with a request timeout.

• Raw HTTP Request Builder

  Build a textual HTTP/1.1 request from explicit URL and headers.

• JSON to Environment File

  Generate quoted dotenv assignments from scalar JSON fields.

• Flat JSON to INI

  Generate one explicit INI section from flat scalar JSON values.

• Flat JSON to TOML

  Generate scalar TOML assignments from flat JSON fields.

• JSON to Java Properties

  Generate escaped .properties assignments from scalar JSON fields.

• Apache Redirect Map Draft

  Generate Redirect 301 directives from explicit old-path/new-URL pairs.

• Nginx Exact Redirect Draft

  Generate exact-location return-301 blocks from explicit URL pairs.

• Content Security Policy Directive Inspector

  Parse CSP directives and report duplicate directive names without changing the policy.

• HTTP Content-Type Parameter Parser

  Parse a media type and simple quoted or token-valued parameters.

• JSON to Go Struct

  Generate a Go struct with JSON tags and safe exported field names.

• JSON to Rust Struct

  Generate a serde-enabled Rust struct with explicit JSON field renames.

• JSON to C Sharp Class

  Generate a C# class with JsonPropertyName attributes and primitive property types.

• JSON to Python TypedDict

  Generate a functional Python TypedDict declaration preserving field names.

• JSON to Kotlin Data Class

  Generate a Kotlin data class with primitive types and numbered field names.

• JSON to GraphQL Object Type

  Generate a GraphQL object type from flat non-null primitive fields.

• Flat JSON to Avro Schema

  Generate a named Avro record schema from flat primitive JSON fields.

• Flat JSON to Protocol Buffers

  Generate a proto3 message with numbered fields for non-null primitive JSON values.

• Flat JSON to XML Schema

  Generate an XSD element sequence from flat primitive field names.

• JSON Record to SQL Table DDL

  Generate an ANSI-style CREATE TABLE draft from flat primitive sample fields.