Free Developer Tools

Every formatter, encoder and validator here runs client-side. That matters more than convenience: you can paste a production JWT, a config file or a database dump into these tools without it ever leaving your machine — which is not true of most online dev utilities.

81 tools in this category · free · no signup · no watermarks

Developer

JSON Formatter & ValidatorBeautify, minify and validate JSON with clear error messages.Base64 Encoder / DecoderEncode text to Base64 or decode it back, with UTF-8 support.URL Encoder / DecoderPercent-encode or decode URLs and query strings safely.

Encoding & Escaping

HTML EncoderEscape text into HTML entities (< > & " ') for safe markup.HTML DecoderDecode HTML entities back into plain, readable text.Escape JSON StringTurn text into a safe, quoted JSON string literal.Escape JavaScript StringEscape text for a JavaScript/TypeScript string literal.Escape SQL StringEscape single quotes for safe SQL string literals.Escape RegexEscape regex metacharacters to match text literally.

Formatters

JavaScript FormatterBeautify and indent messy or minified JavaScript.CSS FormatterBeautify and indent minified or messy CSS.HTML FormatterBeautify and indent HTML markup.SQL FormatterFormat SQL queries with clean indentation and keyword casing.YAML FormatterValidate and re-indent YAML with clear error messages.XML FormatterValidate and pretty-print XML documents.Markdown to HTMLConvert Markdown into clean HTML source.Markdown PreviewWrite Markdown and see it rendered live, side by side.CSV to JSONConvert CSV data into a JSON array of objects.JSON to CSVConvert a JSON array of objects into CSV.Regex TesterTest regular expressions live with match highlighting.

JSON / XML / YAML Data Tools

JSON MinifierStrip whitespace to minify JSON.JSON ViewerExplore JSON as a collapsible, colour-coded tree.JSON Key SorterSort JSON object keys alphabetically.JSON to YAMLConvert JSON into YAML.YAML to JSONConvert YAML into JSON.JSON to XMLConvert JSON into XML.XML to JSONConvert XML into JSON.JSON DiffCompare two JSON documents and highlight differences.XML MinifierValidate and minify XML by removing whitespace.XML Escape / UnescapeEscape or unescape XML special characters.XML ViewerExplore XML as a collapsible tree.XML DiffCompare two XML documents.XPath TesterTest XPath expressions against an XML document.YAML ViewerExplore YAML as a collapsible tree.YAML DiffCompare two YAML documents.

CSS Tools

CSS MinifierMinify CSS by removing comments and whitespace.CSS Gradient GeneratorBuild linear and radial CSS gradients with a live preview.CSS Box Shadow GeneratorCreate box-shadow CSS visually with a live preview.CSS Border Radius GeneratorVisually craft border-radius CSS per corner.CSS Clip Path GeneratorGenerate clip-path shapes with a live preview.CSS Flexbox GeneratorExperiment with flexbox properties and copy the CSS.CSS Grid GeneratorGenerate CSS grid layouts with a live preview.

JS / SQL / URL

JavaScript MinifierMinify JavaScript with Terser.JavaScript ValidatorCheck JavaScript for syntax errors.JavaScript UnescapeDecode escaped JavaScript strings.SQL MinifierMinify SQL by removing comments and whitespace.Query String ParserParse a URL query string into key/value pairs and JSON.Query String BuilderBuild an encoded query string from key/value pairs.

Base & Text Encoding

Base32 Encoder / DecoderEncode and decode Base32 (RFC 4648).Base58 Encoder / DecoderEncode and decode Base58 (Bitcoin alphabet).Base85 Encoder / DecoderEncode and decode Base85 (Ascii85).UTF-8 ConverterConvert text to and from UTF-8 hex bytes.UTF-16 ConverterConvert text to and from UTF-16 code units.UTF-32 ConverterConvert text to and from UTF-32 code points.

Hash & Crypto

MD5 GeneratorGenerate an MD5 hash of text.HMAC GeneratorGenerate an HMAC signature with SHA-1/256/384/512.BCrypt GeneratorHash and verify passwords with BCrypt.CRC32 CalculatorCompute the CRC32 checksum of text.Adler-32 CalculatorCompute the Adler-32 checksum of text.

JWT & Security

JWT DecoderDecode and inspect JWT header, payload and signature.JWT EncoderCreate and sign a JWT with HS256/384/512.OAuth URL BuilderBuild an OAuth 2.0 authorization URL.Basic Auth GeneratorGenerate an HTTP Basic Authentication header.

Regex & API

Regex GeneratorReady-made regular expressions for common tasks.Regex Cheat SheetA quick reference for regular-expression syntax.Regex ExplainerBreak a regex into plain-English tokens.HTTP Header ParserParse raw HTTP headers into a readable table.cURL BuilderBuild a cURL command from a form.cURL to FetchConvert a cURL command into JavaScript fetch() code.cURL to AxiosConvert a cURL command into axios code.Postman Collection ViewerList the requests inside a Postman collection.

Dates & Misc

Date FormatterFormat a date with custom tokens and export formats.ISO 8601 ConverterConvert between ISO 8601, Unix and human dates.Markdown Table GeneratorBuild Markdown tables in a visual grid.MIME Type CheckerLook up MIME types by extension and vice versa.MIME DetectorDetect a file's true type from its magic bytes.

Misc

Sitemap.xml GeneratorGenerate a sitemap.xml from a list of URLs.Open Graph PreviewPreview and generate Open Graph tags.Meta Tag GeneratorGenerate SEO, Open Graph and Twitter meta tags.Schema.org GeneratorGenerate Schema.org JSON-LD structured data.Favicon GeneratorGenerate a favicon pack from an image.

Why these tools run in your browser

Most online tools work by uploading your file to a server, processing it there, and sending the result back. That means a copy of your document exists on a machine you do not control, governed by a retention policy you did not write. Toolsnest inverts that: the code is downloaded to you, and your file stays put. You can verify this yourself — open your browser's Network tab, run any tool on this page, and watch that no request carries your file.

No accounts, no limits, no watermarks

Because there is no server doing the work, there is no per-task cost to recover — so there is no daily task cap, no queue, no watermark on the output and no upgrade prompt. Batch sizes are limited only by your own device's memory.

Explore more

Browse the full catalogue of every Toolsnest tool, or read the guides for step-by-step walkthroughs.