AltCatch
Audit any page for missing alt text and broken images, then export clean Markdown reports
developeraccessibilityalt-text
89 free tools · 100% client-side · no signup
All Free Online Developer Tools & Utilities
Browse all 89 free developer utilities — encoders, formatters, converters, calculators, and design tools. Everything runs in your browser, with no signup and nothing uploaded.
- Instant & free
- Runs in your browser
- Lightweight & fast
- Fully responsive
⌘ K
Category
Active:Developer
30 Tools found
Showing tools in Developer
Cron Expression Builder
Write, parse, and validate any standard 5-field cron schedule with next-fire times and plain-English description
developercronscheduler
CSS Beautifier
Format minified CSS into clean, readable code with proper indentation
developercssbeautifier
CSS Minifier
Minify and compress CSS code to reduce file size
developercssminifier
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes instantly
developerhashmd5
HMAC Generator
Compute HMAC signatures (SHA-1, SHA-256, SHA-384, SHA-512) via the Web Crypto API with hex, Base64, and Base64URL output. Used for JWT HS256, AWS Sig V4, GitHub webhooks, and API request signing.
developerhmachmac sha256
HTML Formatter
Format and beautify HTML code with proper indentation
developerhtmlformatter
HTML to JSX
Convert HTML to React JSX: 30+ attribute renames (class→className, for→htmlFor, event handlers to camelCase), inline styles to object syntax, void elements self-closed, HTML comments translated.
developerhtml to jsxreact converter
HTTP Status Codes
Complete searchable reference for every HTTP status code (1xx-5xx) with plain-English descriptions, typical use cases, and RFC 9110 citations — including WebDAV, rate-limit, and captive-portal extensions
developerhttp status codesrest api
JavaScript Minifier
Minify and compress JavaScript code for production
developerjavascriptminifier
JSON Diff
Semantic JSON comparison — walk two JSON trees and emit path-indexed added / removed / changed records. Ignores whitespace and key order. Distinct from line-by-line text Diff Checker.
developerjson diffjson compare
JSON Formatter
Format, validate, and beautify JSON data with advanced error handling
developerjsonformatter
JSON Schema Generator
Generate JSON Schema (Draft 2020-12, 2019-09, or Draft-07) from any JSON example with inferred types, required fields, and detected string formats (email, uuid, date-time, uri, ipv4).
developerjson schemadraft 2020-12
JSON to TypeScript
Generate clean TypeScript interfaces from any JSON with recursive nested types, array unions, and configurable style
developertypescriptjson
JSON to YAML Converter
Bidirectional JSON ↔ YAML converter with custom serializer and YAML 1.2 subset parser tuned for real-world configs (Kubernetes, GitHub Actions, Docker Compose, Ansible). Inline error reporting and one-click direction toggle.
developerjson to yamlyaml to json
JWT Decoder
Decode JSON Web Tokens to inspect header, payload, and claims with expiration check — 100% client-side
developerjwtdecoder
LLM Token Counter
Estimate token count and API cost for any prompt across GPT-4, GPT-4o, Claude Opus 4.7, Claude Sonnet 4.6, Claude Haiku, Gemini 1.5 Pro and Flash. Live count, 2026 pricing, context-window utilization bar
developertoken countergpt tokens
Markdown to HTML
Convert Markdown to clean HTML with side-by-side rendered preview. Supports CommonMark essentials plus GFM strikethrough, fenced code, and tables. 100% client-side custom parser.
developermarkdown to htmlmd converter
Meta Tag & OG Previewer
Paste HTML and see live Google SERP, X, Facebook, and LinkedIn previews with length checks and per-rule SEO validation
developerseometa tags
Number Base Converter
Convert numbers between binary, octal, decimal, hexadecimal, and any base 2-36 with BigInt precision and two's complement support
developerbinaryhex
Open Graph Tag Generator
Generate HTML <head> meta tags for Open Graph (Facebook/LinkedIn/Slack), Twitter Card, description, canonical, and theme-color from a simple form. Character-count guidance based on 2026 platform best practices.
developeropen graphog tags
Password Generator
Generate strong, secure passwords with custom options
developerpasswordgenerator
Password Strength Meter
Offline password strength tester with entropy math, breach-corpus check, pattern detection, and crack-time estimates
developerpasswordsecurity
Random Number Generator
Cryptographically-strong random integers in any range with no modulo bias — up to 10,000 numbers, optional uniqueness and sort
developerrandomrng
Regex Tester
Test and debug regular expressions with live matching
developerregextester
SQL Formatter
Format and beautify SQL queries with syntax highlighting
developersqlformatter
URL Parser
Decompose any URL into protocol, host, port, path segments, query parameters (as a table), and hash using the native WHATWG URL parser. Decoded and raw values shown side-by-side.
developerurl parserquery parameters
UUID Generator
Generate unique UUIDs (v1, v4, v5) for your applications
developeruuidgenerator
XML Formatter
Beautify or minify XML with native DOMParser validation. Works on SOAP envelopes, RSS feeds, sitemaps, Android string resources, SVG, and Office Open XML. 100% client-side.
developerxml formatterxml beautifier
YAML Validator
Validate, format, and convert YAML with line-precise errors — ideal for GitHub Actions, Kubernetes, Docker Compose, and Ansible
developeryamlvalidator
Why developers use Toolk
Toolk bundles 89 single-purpose utilities that run entirely in your browser. Whether you're beautifying a JSON API response, formatting a SQL query, or encoding data to Base64, each tool does one job, instantly — no signup, nothing uploaded.
Your data never leaves your device
Most online tools send your input to a server to process it — a real risk when you're pasting private keys, customer records, or proprietary code. Toolk runs every operation client-side in JavaScript, so nothing you type or upload is transmitted anywhere.
Built for real workflows
Beyond formatters, the catalogue includes security tools like a password generator and SHA-256 hash generator, plus design utilities such as color palette generators and image encoders — all aligned with W3C standards.
Frequently asked questions
Are these developer tools really free?
Yes — every tool on toolk is currently free to use, with no signup and no usage limits. The project is funded by its maintainer as a community resource.
Do I need to sign up to use the tools?
No signup or registration is required. You can use any of our tools immediately, as many times as you want, with no personal information collected.
Is my data secure when using toolk?
Absolutely. All processing happens locally in your browser. We do not transmit your input data to our servers, ensuring your sensitive development data stays private and secure.
What categories of tools do you offer?
We offer a wide range of tools across categories like Data Processing (JSON, SQL, Base64), Text Utilities (Word Counter, Case Converter), Design (Color Palette), and Security (Password Generator, Hash Generator).
Free, fast, and privacy-first
Every tool is free for both personal and commercial use, with no account and no usage limits. Read more about why Toolk is free and how the privacy model works.
About ToolkNeed a different tool?
Browse all 89 free, in-browser tools — or tell us what we should build next.