Developers Tools — 40 Free Online, No Sign-Up

JSON Formatter

Format, validate, minify, and sort JSON. Error messages with line numbers. Escape and unescape strings.

Base64 Encoder/Decoder

Encode and decode Base64. Works with text and files. URL-safe variant supported.

CSV ↔ JSON

Convert between CSV and JSON. Handles quoted fields, custom delimiters, auto-detects direction.

SQL Formatter

Format messy SQL queries. Indented clauses, keyword case, comma style. Handles comments and strings correctly.

JSON Diff

Compare two JSON documents structurally. See added, removed, and changed values per path.

JSON Schema Generator

Paste a JSON sample, get a JSON Schema. Auto-detects types, formats, enums, required fields.

YAML ↔ JSON Converter

Convert YAML to JSON or JSON to YAML. Format and validate. Handles anchors, aliases, multi-line strings.

XML Formatter & XML ↔ JSON

Format, minify, and convert XML. Handles attributes, namespaces, CDATA, processing instructions.

HTTP Status Code Reference

Every HTTP status code with common causes and what to do. Searchable, filterable, jump-by-code.

HTML Minifier & Beautifier

Collapse whitespace, strip comments and inline CSS/JS — or beautify back with consistent indentation.

CSS Minifier & Beautifier

Strip comments and whitespace for production, or re-expand minified CSS into readable indented form.

JS Minifier & Beautifier

Compact JavaScript by removing comments and whitespace, or format minified JS with consistent indentation.

URL Parser

Break any URL into protocol, host, port, path, query, fragment. See each query param on its own line. Decode on.

User-Agent Parser

Paste any User-Agent string to see the browser, engine, OS and device it identifies as. Detects major edge cases.

URL Encoder/Decoder

Encode and decode URL components. Parse query strings into a readable table.

Regex Tester

Test JavaScript regex with live match highlighting, capture groups, and replace.

HTML Entity Encoder/Decoder

Encode special characters to HTML entities and back. Named or numeric, safe or full.

Binary ↔ Text Converter

Convert text to 8-bit binary and back. UTF-8 aware so emojis and accents round-trip correctly.

UUID Generator

Generate cryptographically random v4 UUIDs. Batch up to 1000 at a time. Multiple formats.

.gitignore Generator

Combine curated templates for languages, frameworks, IDEs, and operating systems. Inlined, no external fetches.

CIDR / Subnet Calculator

Calculate IPv4 subnet ranges, masks, host counts, and binary representations from any CIDR notation.

chmod / Permission Calculator

Convert between octal, symbolic, and chmod commands. Visual checkboxes for user/group/other.

Google SERP Preview

See how your page appears in Google — desktop + mobile snippets with title (60 char) and description (155 char) truncation.

Robots.txt Generator

Visual builder for robots.txt — user-agent rules, allow / disallow paths, sitemap link, crawl-delay. Block AI crawlers preset.

Sitemap.xml Generator

Paste URLs — get a valid sitemap.xml with lastmod, changefreq, priority. Download as file.

Schema Markup Generator

JSON-LD for Article, FAQ, Product, LocalBusiness, Recipe, HowTo, Event, Organization, BreadcrumbList.

Markdown TOC Generator

Paste Markdown — get a table of contents with GitHub-style anchor links. Configurable depth.

JSONPath Tester

Write JSONPath queries ($.foo[*].bar), see matches live. Filter expressions + slices supported.

JSON to TypeScript

Generate TypeScript interfaces from JSON with inferred types and nested interfaces.

HTML to JSX

Convert HTML to React JSX — className, style objects, self-closing tags, camelCased attributes.

cURL Builder

Build a copy-paste curl command from a form: method, URL, headers, JSON body, auth.

String Escape / Unescape

Escape or unescape strings for JSON, JS, HTML, URL and backslash sequences. Two-way.

Nano ID & ULID Generator

Generate Nano IDs and sortable ULIDs in bulk. Cryptographically random, URL-safe.

SVG Optimizer

Minify SVG, strip editor cruft + metadata, export as optimized SVG, CSS data-URI or img tag.

Test Credit Card Numbers

Luhn-valid fake card numbers for testing payment forms. Visa/MC/Amex/Discover. Validator too.

Base58 Encode / Decode

Bitcoin-style Base58 (no confusing 0 O I l). Encode text or decode back. Two-way.

Discord Timestamp

Generate dynamic Discord timestamp codes for every style. Renders in local time.

HTML Table Generator

Build HTML table markup: rows, columns, header row, borders, striping. Live preview.

URL Status Checker

HTTP status code + full redirect chain (301 → 200) for any URL. Find broken links.

HTTP Header Checker

Inspect any URL's response headers + security-header checklist (HSTS, CSP, XFO).

About this toolkit

A comprehensive developer utility belt — JSON / YAML / XML / SQL formatters, CSV ↔ JSON, regex tester, URL encoder + parser, HTML / CSS / JS minifiers, Base64, UUID, .gitignore generator, CIDR / chmod calculators, HTTP status reference, SEO helpers (SERP preview, robots.txt builder, sitemap.xml generator, JSON-LD schema generator), Markdown TOC, JSONPath tester, and more.

Who uses these tools

Data format conversion & formatting — JSON ↔ YAML ↔ XML, CSV ↔ JSON, SQL formatter, JSON diff, JSON schema generator, JSONPath tester.
Encoding & identifiers — Base64 encode / decode (text + files), URL encode / decode, URL parser, user-agent parser, UUID v1/v4/v7, HTML entities, binary ↔ text.
Code minification — HTML / CSS / JS minifiers — strip whitespace, comments, optional name mangling. Counterpart to formatters.
Pattern testing — Regex tester with live highlights, flag toggles, match groups breakdown.
Network & system reference — .gitignore templates, CIDR notation calculator, chmod octal ↔ symbolic converter, HTTP status code reference.
SEO & meta — SERP preview (how your title + meta description will look in Google results), robots.txt builder, sitemap.xml generator, JSON-LD schema generator (Article, FAQ, BreadcrumbList, WebPage, Organization, Product), Markdown TOC generator.

Frequently asked questions

Are these developer tools really free?

Yes — every tool in the Developers category is free, no sign-up, no usage limits, no API keys required.

Do any of the tools require an API key or backend?

No. Everything runs in your browser via JavaScript. Even the JSON / YAML / XML formatters use locally-bundled parsers — your source code never leaves your device.

Can I trust the regex tester with sensitive patterns?

Yes — the regex tester runs entirely in your browser's JavaScript engine. Neither the regex nor the test input is sent anywhere.

Why both formatters and minifiers?

Different ends of the same workflow. Minify for production (smaller files, faster loads). Format / beautify when reading minified code or debugging.