Dev Stack Kit

Your ultimate toolkit for developers

53 free online developer tools across security, code conversion, formatting, frontend, and data generation — fast, secure, and easy to use.

Formatters & Parsers

JSON ParserValidate, format, tree-view, and save JSON entries.JSON Schema ValidatorValidate JSON documents against a schema with path-specific errors.JSONPath TesterQuery JSON with expressions and inspect matched values.XML/XSD ValidatorValidate XML structure and required XSD elements locally.JSON ↔ TOML ConverterConvert common configuration data between JSON and TOML.URL ParserInspect URL parts, query parameters, and build URLs in reverse.Query String ParserParse and build URL-encoded key-value query strings.REST API TesterSend browser-based HTTP requests and inspect responses.JSON BeautifierQuick JSON format/minify — no save, just fast pretty-printing.JSON CompareDiff two JSON documents and see what changed, line by line.Text CompareCompare two blocks of text and highlight the differences.XML FormatterFormat, minify, and validate XML documents.SQL FormatterFormat and prettify SQL across ANSI, MySQL, and PostgreSQL.GraphQL Query FormatterPrettify and format GraphQL queries and mutations.JSON ↔ YAML ConverterConvert between JSON and YAML formats instantly.cURL to Code ConverterConvert a curl command into fetch, Axios, or Python code.Code Diff CheckerSide-by-side line diffing for code snippets.Byte ParserParse byte arrays, extract ranges, and convert values.

Security & Auth

JWT DecoderDecode JWT headers, payloads, and check expiration status.Encode / DecodeBase64 and URL encode/decode text instantly.Hash GeneratorGenerate MD5, SHA-1, SHA-256, and SHA-512 hashes live.Password GeneratorGenerate secure passwords, API keys, and secret tokens.Password Strength CheckerCheck password criteria and estimated offline crack time locally.Certificate DecoderInspect local PEM X.509 certificate fields and fingerprints.IBAN ValidatorCheck IBAN country format and checksum locally.CSP Header GeneratorVisually build a Content-Security-Policy HTTP header.AES-256 Encrypt & DecryptEncrypt and decrypt text with a passphrase using AES-256.Base64URL & Base32 ConverterConvert text to/from Base64, Base64URL, and Base32.RSA Key Pair GeneratorGenerate a 2048-bit RSA key pair and encrypt/decrypt text.

Code & Conversion

Unix Timestamp ConverterConvert Unix epoch timestamps to dates and back.Timezone ConverterConvert a date and time across named IANA timezones.Number / Byte FormatterFormat numbers and convert raw bytes into readable units.Cron ParserParse cron expressions into plain English and next run times.Base ConverterConvert numbers between binary, octal, decimal, hex, and more.Case ConverterConvert text between camelCase, snake_case, and more.Slug GeneratorGenerate SEO-friendly URL slugs and analyze text.Subnet CIDR CalculatorCalculate IP ranges, netmasks, and broadcast addresses.HTML Entity Encoder/DecoderConvert raw text to HTML entities and back.

Frontend & Design

User-Agent ParserExtract browser, OS, engine, and device from a UA string.SVG OptimizerClean and minify SVG code, stripping editor metadata.Color ConverterConvert HEX/RGB/HSL/OKLCH and check WCAG contrast.Color Blindness SimulatorPreview colors and images under vision deficiency modes.CSS Effects GeneratorBuild CSS gradients and box shadows with live previews.Meta Tag / Open Graph PreviewPreview social link cards and generate share metadata.Image Resizer / CropperResize, crop, and download images locally with Canvas.Base64 Image ConverterConvert images to Base64 data strings and vice versa.Favicon GeneratorGenerate favicon.ico and web app icons from an image.

Data Generation & Utilities

GUID GeneratorGenerate one or many random UUIDs with format options.Dummy Data GeneratorGenerate mock JSON data for presets or a custom schema.String Replacer / List CompareBulk replace text or compare two line-based lists.Lorem Ipsum GeneratorGenerate placeholder text by words, sentences, or paragraphs.Robots.txt GeneratorBuild and validate a custom robots.txt file.QR Code GeneratorGenerate QR codes from text or URLs.

Free Browser-Based Developer Utility Suite

DevStackKit is a 100% free, ad-supported developer utility hub with no Pro versions, subscriptions, usage limits, or paywalls. Most of the 53 tools process data locally inside your browser using JavaScript and WebAssembly—your code snippets, payloads, and tokens stay on your device. The REST API tester sends requests to URLs you specify. Tools you've visited work offline once cached; install DevStackKit as an app for better offline support on Android, Windows, macOS, and iOS.

It is also a practical collection of online utility tools, free coding tools, and dev helper tools for everyday tasks: format data, inspect requests, convert encodings, check security values, generate test content, and prepare frontend assets without installing a separate utility for each job.

Explore our core utility categories: Formatters & Parsers, Security & Auth, Code & Conversion, Frontend & Design, and Data Generation & Utilities. Featured tools include JSON Parsers, JWT Decoders, SQL Formatters, Base64 converters, Unix timestamp utilities, and Code Diff Checker.

Frequently Asked Questions

Are my inputs stored on your servers?

Most tools process data locally in your browser. The REST API tester sends requests to the URL you enter. Nothing is stored on our servers.

Is DevStackKit free to use?

Yes, DevStackKit is 100% free and ad-supported with unlimited usage. There are no paid tiers or paywalls.

Does DevStackKit work offline?

Tools you've visited work offline after you've used them (the app caches them automatically). Install DevStackKit as an app for better offline support. The REST API tester requires internet to reach external URLs.

What tools are included?

DevStackKit includes JSON parsers, JWT decoders, SQL formatters, Cron expression parsers, Base64 converters, Unix timestamp converters, Code Diff Checker, and more.

Can I install DevStackKit as an app?

Yes. Install on Android, Windows, macOS with Chrome/Edge; on iPhone/iPad via Safari. See the install steps on the About page.