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Free Developer Tools
Format and convert code, inspect encoded data and certificate requests, generate CSS, or decode a Data Matrix image.
65 free toolsNo sign-upBrowser-based
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Choose by input format and output goal. Formatting changes presentation; decoding displays data and does not establish trust. Each page explains its supported formats and limits.
Developer Tools
65 toolsUUID GeneratorGenerate random version 4 UUIDs in your browser.PX to REM ConverterConvert CSS pixels to rem units using your root font size.IPv4 Subnet CalculatorFind network, mask, broadcast, and usable address range.CSS Border Radius GeneratorSet four corner radii and copy ready-to-use CSS.CSS Box Shadow GeneratorAdjust offset, blur, spread, colour, and opacity with a live preview.CSS Gradient GeneratorChoose colors and an angle, then copy a CSS gradient.HMAC GeneratorGenerate an HMAC from a UTF-8 message and secret key.Cron Expression GeneratorBuild a standard five-field cron schedule.Regex TesterTest a JavaScript regular expression with match positions.Punycode ConverterConvert Unicode hostnames to ASCII Punycode and back.Base64 Encode DecodeEncode Unicode text to Base64 or decode UTF-8 Base64 text.URL Encoder DecoderEncode or decode a URL component or a complete URI.SQL FormatterFormat SQL using the dialect and keyword case you choose.HTML MinifierReduce HTML whitespace and optionally remove comments.XML FormatterFormat XML with indentation while keeping mixed content together.JWT DecoderInspect the header and payload of a compact JWT without verifying its signature.CSS MinifierMinify CSS while retaining strings, custom properties, and rule order.TOML to JSON ConverterConvert TOML tables, arrays, and values into formatted JSON.JSON to PHP Array ConverterGenerate a PHP array expression from JSON without running code.SVG to CSS ConverterConvert self-contained SVG markup into a CSS background data URI.YAML ValidatorValidate YAML 1.2 syntax, duplicate keys, and bounded alias references.JSON to Python Dataclass GeneratorInfer nested Python dataclass definitions from JSON example records.CSR DecoderInspect a PEM PKCS#10 certificate request, subject, key, and requested extensions.Data Matrix DecoderDecode an ECC200 Data Matrix from a clear image locally.HTML SanitizerRemove scripts, event handlers and unsupported markup from basic HTML. Review the cleaned fragment and a contained preview.HTML to JSX ConverterConvert an HTML fragment to JSX with React attribute names, style objects and self-closing elements.JSON Schema Generator from JSONInfer a draft-07 JSON Schema from a sample object or object array, then review it before using it as a contract.JSON Diff CheckerCompare two JSON values by structure. See changed paths without treating object key order as a difference.TOML to YAML ConverterConvert TOML tables, arrays and values into YAML 1.2. Keep exact integers and review how dates are represented.JSON Schema ValidatorValidate JSON against a draft-07 or 2020-12 schema. Review error paths without sending the documents to a server.JSON to Rust Struct GeneratorGenerate nested Rust model definitions from a JSON example. Review the inferred fields, then copy or download the source.JSON to Go Struct GeneratorGenerate nested Go model definitions from a JSON example. Review the inferred fields, then copy or download the source.JSON to Swift Model GeneratorGenerate nested Swift model definitions from a JSON example. Review the inferred fields, then copy or download the source.JSON to Kotlin Data Class GeneratorGenerate nested Kotlin model definitions from a JSON example. Review the inferred fields, then copy or download the source.JSON to C# Class GeneratorGenerate nested C# model definitions from a JSON example. Review the inferred fields, then copy or download the source.OpenAPI ValidatorCheck a local Swagger 2.0, OpenAPI 3.0 or OpenAPI 3.1 document for schema errors and broken internal references. Read the reported paths without querying your API.JSON to Java class GeneratorGenerate plain Java model classes from a JSON object or object array. Download a ZIP with separate class files, then review inferred types and add your serializer mapping.WOFF to TTF ConverterConvert a supported WOFF font to a TrueType container while keeping its table content. Use a font you have permission to convert and review the downloaded TTF.JSON to Protobuf ConverterDraft proto3 messages from a JSON sample. Review inferred scalar types, nested messages and numbered fields before adopting the schema in a protocol.JSON Schema to TypeScript ConverterGenerate TypeScript definitions from a local JSON Schema. Structural types and internal definitions become source code; runtime validation rules still need a validator.JSON to TypeScript interface GeneratorInfer TypeScript interfaces from a JSON sample. Copy or download the nested definitions, then review optional fields and number precision against your actual API.XML Diff CheckerCompare two XML documents by parsed structure. Read changed paths while ignoring attribute order and whitespace used only for indentation.TTF to WOFF ConverterPackage a supported TrueType font as compressed WOFF. The conversion changes the container while retaining supported font tables; check font usage rights before converting.SVG to TTF ConverterTurn a simple SVG path outline into a one-glyph TrueType icon font. Choose a font family and Unicode code point, then review the saved glyph.WOFF2 to WOFF ConverterDecode a supported WOFF2 font and save it as WOFF. The codec runs locally; variable, color and CFF fonts are outside this tool’s supported scope.OTF to TTF ConverterConvert supported OpenType CFF1 outlines into a TrueType font. Review curve approximation and lost hinting or shaping data before using the result.CSV To SQL ConverterGenerate CREATE TABLE and INSERT statements from CSV records. Choose SQLite or PostgreSQL, keep cells as text and review the source before executing it yourself.Font converterA static TTF, WOFF or WOFF2 font. Detect a supported TrueType container and repackage its SFNT tables into the selected output.HTML ValidatorHTML markup diagnostics with line and column locations. Run bundled html-validate rules against the supplied HTML source without executing it.ASCII to Text ConverterValidate whitespace- or comma-separated integer codes from 0 to 127 and map them to ASCII characters.Binary To Text ConverterGroup binary digits into eight-bit bytes and decode them as strict UTF-8.Hex To Text ConverterValidate pairs of hexadecimal digits and decode the bytes as strict UTF-8.HTML Entity Encoder DecoderEncode ampersands, angle brackets and quotes, or decode recognized HTML character references without executing markup.Password GeneratorChoose each character with unbiased browser cryptographic random integers; include at least one character from each selected group.REM to PX ConverterPixels = REM value × root font size.Passphrase GeneratorDraw independent words with unbiased cryptographic randomness from the disclosed 256-word pool.Password Entropy CheckerEstimate bits as password length × log2 of the detected character-pool size.Unicode Escape ConverterEncode UTF-16 code units as Unicode escapes, or parse a JSON string body without evaluating code.JavaScript BeautifierParse and format source with a pinned local Prettier browser bundle.GraphQL FormatterParse and format source with a pinned local Prettier browser bundle.HTML FormatterParse and format source with a pinned local Prettier browser bundle.JavaScript MinifierParse JavaScript with Terser and print compact syntax with compression and name mangling disabled.SQL MinifierTokenize SQL strings, quoted identifiers and comments, then collapse whitespace outside those regions.XML MinifierRemove line-break indentation from element-only XML; keep inline spaces, mixed text and xml:space="preserve".Encode File To Base64 ConverterEncode arbitrary file bytes as standard Base64, without guessing a text encoding.
How to choose
UUID Generator creates random version 4 identifiers using the browser's secure random source. The IPv4 Subnet Calculator accepts a dotted-decimal address and CIDR prefix, then shows the network, mask, address count, and usable range. A /31 follows the point-to-point convention; a /32 is one host route.
PX to REM converts values against the root font size you enter. The border-radius and box-shadow generators produce copyable CSS declarations and show a live preview. Check the generated CSS in your own layout, since surrounding styles and browser rendering can affect appearance.
XML, SQL, CSS, and HTML tools format or minify text. TOML to JSON converts table structures, YAML Validator checks syntax, and JSON generators produce PHP arrays or inferred Python dataclasses. Generated code is an example to review, not a runtime validation contract.
JWT Decoder displays unverified header and payload data. CSR Decoder can inspect a PKCS#10 self-signature, which does not prove CA trust or domain ownership. Data Matrix Decoder reads one ECC200 symbol from an image and leaves decoded URLs as text.
Common questions
Does the subnet tool support IPv6?
No. It calculates IPv4 addresses and CIDR prefixes from /0 to /32.
Can I copy generated values?
Yes. The UUID and CSS tools provide a copy button for their output.