Do any of these tools send my code or data to a server?

No. Every tool in this list processes data entirely in your browser using standard JavaScript APIs. JSON, code, passwords, JWT tokens, and API credentials never leave your device. Security-sensitive tools like Hash Generator and Password Generator use the browser's built-in SubtleCrypto API, which runs natively without network calls.

Can I test real API endpoints with the API Request Generator?

Yes. The API Request Generator & Tester lets you build requests with custom headers, body (JSON, form data, raw), authentication, and query parameters, then execute them live in the browser and inspect the response status, headers, and body. It generates equivalent code in 12 languages so you can copy a working snippet for your project.

What JWT claims does the JWT Decoder show?

The JWT Decoder splits any JWT into its three parts, base64-decodes the header and payload, and displays all claims with human-readable descriptions — including exp (expiry with live countdown), iat (issued at), nbf, sub, aud, iss, and any custom claims. It also verifies HS256 signatures if you provide the secret.

What UUID formats does the UUID generator support?

The UUID / ULID / NanoID generator supports UUID v4 (random), UUID v7 (time-ordered, sortable), UUID v1 (time-based with MAC address), ULID (Universally Unique Lexicographically Sortable Identifier), and NanoID with a custom alphabet. It generates up to 1,000 IDs at once with uppercase, no-hyphens, and copy-all options.

How does the Diff Checker work?

Paste two text blocks (code, JSON, prose, config) into the left and right panels. The tool uses LCS (Longest Common Subsequence) diffing to identify added, removed, and unchanged lines. Switch between split view (side by side), unified view (GitHub-style), and character-level inline highlighting to see exactly what changed.

Can I build fake API responses for frontend development?

Yes. The API Mock Generator lets you define JSON schema structures and generates realistic fake data (names, emails, dates, IDs, booleans). Export as a JSON Server db.json file to run a local mock REST API, or as a Postman collection for sharing with your team.

Free Online Developer Tools

Format JSON, test APIs, generate code, decode tokens, convert data formats, and debug regex — all browser-based, no signup.

📄PDF Tools 🎨CSS Tools {}Developer Tools 🖼️Image Tools ¶Text Tools ◑Design Tools

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JSON Formatter

Format & validate

Format, validate, minify, and syntax-highlight JSON. Live parsing with sort keys and download support.

⊞

JSON Table Viewer

Tabular JSON explorer

Visualize JSON arrays as tables. Filter, sort, paginate, toggle columns, and export as CSV.

📊

JSON Dashboard Generator

Charts · filters · React export

Paste any JSON or API response → instant stat cards, bar/line/pie charts, category filters, sortable table, and a complete React dashboard with Recharts. No setup required.

</>

HTML Formatter

Prettify HTML, CSS & JS

Paste HTML and format it instantly with proper indentation. Prettifies inline <style> CSS and <script> JS. Line numbers + history.

✦

Tailwind Formatter

Sort & group classes

Sort, deduplicate, and group Tailwind CSS classes by category. Flat and grouped output views.

⊛

SQL Formatter

Beautify & minify SQL

Format and beautify SQL queries with proper indentation, keyword casing, and syntax highlighting. Minify SQL, dialect support for MySQL, PostgreSQL, SQLite & SQL Server.

⟺

Diff Checker

Compare text & code

Compare two texts side-by-side with LCS-based diffing. Split, unified, and char-level inline modes.

</>

Regex Tester

Test & debug patterns

Live regex match highlighting, capture group table, replace mode with $1/$<name> references, 10 presets, and a quick-reference panel. All JS flags supported.

⇄

API Request Generator & Tester

Generate · Test · 12 langs

Generate HTTP request code in 12 languages and test APIs live in the browser — Fetch, Axios, XHR, Node.js, cURL, Python, PHP, Ruby, Go, C#, Jest, Pytest. GraphQL, env vars, history & Postman import.

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API Mock Generator

Fake REST API with JSON schema

Build fake REST API endpoints with realistic mock JSON. Auto-generate fake data, export as JSON Server db.json or Postman collection. Free for frontend devs.

UUID / ULID / NanoID

v4, v7, v1, ULID, NanoID

Generate UUID v4, v7, v1, ULID, and NanoID in bulk. Uppercase, no-hyphens, custom NanoID alphabet. Up to 1000 IDs, copy all or download. 100% browser, no sign-up.

🔑

Password Generator

Secure & entropy-scored

Generate cryptographically secure passwords, passphrases, PINs, and memorable passwords. Live entropy meter, crack-time estimate, bulk generation, and copy history.

Hash Generator

MD5 · SHA-256 · SHA-512

Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes from text or files. HMAC mode, hash verification, uppercase toggle, copy-all. 100% client-side.

B64

Base64 Encoder/Decoder

Encode & decode instantly

Encode text or files to Base64 and decode Base64 strings back to text or images. Standard, URL-safe, and MIME variants. 100% client-side.

JWT

JWT Decoder

Decode & verify tokens

Decode JWT header and payload, read all claims with descriptions, verify HS256 signatures, and check expiry with a live countdown. 100% client-side.

⌗

URL Encoder/Decoder

Percent-encode & decode

Encode and decode URLs and query strings. Supports encodeURIComponent (query params) and encodeURI (full URLs). Highlights %XX sequences live.

⏱

Timestamp Converter

Epoch ↔ date, batch, timezones

Convert Unix timestamps to ISO 8601, UTC, RFC 2822, relative time and more. Supports seconds, milliseconds, microseconds. Timezone picker, batch converter, live clock.

⏰

Cron Expression Builder

Visual cron generator & scheduler

Build and validate cron expressions visually. Point-and-click field builder, instant human-readable descriptions, next 6 run times, 16 presets, and full POSIX syntax support.

⇄

YAML ↔ JSON Converter

Bidirectional, auto-detect

Convert YAML to JSON or JSON to YAML instantly. Auto-detects input format, syntax-highlighted output, sort keys, copy & download. Full YAML 1.2 support.

⇄

CSV ↔ JSON Converter

Table preview & type inference

Convert CSV to JSON or JSON to CSV instantly. Auto-detects format, infers types, live table preview, multiple delimiters, copy & download. RFC 4180 compliant.

📸

Code Screenshot

Beautiful code images

Turn any code snippet into a stunning PNG. 9 themes, 22 languages, macOS/Windows/Terminal frames, gradient backgrounds. Download at 1×/2×/3× scale.

◈

Meta Tag Generator

SEO · OG · Twitter · JSON-LD

Generate complete meta tag sets from page details. Live Google SERP, Facebook OG, and Twitter card previews. Export as HTML, Next.js metadata, React Helmet, Vue/Nuxt, Astro, or JSON-LD.

⇄

HTML → JSX Converter

Convert HTML to React

Convert HTML to React JSX. Handles className, htmlFor, camelCase events, self-closing tags, and inline styles.

JSON → TypeScript

Interface & type generator

Paste JSON and get TypeScript interfaces or type aliases instantly. Handles nested objects, arrays of objects, optional fields, null safety, export keyword, and custom root names.

⬡

Responsive Preview

Test any screen size

Preview any website at 8 screen sizes from 320px mobile to 1920px wide. Zoom controls and device tabs.

M↓

Markdown Editor

Live preview & GFM export

Write Markdown with a real-time GitHub Flavored Markdown preview. Toolbar shortcuts, localStorage auto-save, export as .md or standalone .html. 100% browser, no sign-up.

About Developer Tools

These tools cover the everyday workflows of front-end and full-stack developers: formatting, validation, conversion, testing, and encoding — all running entirely in the browser with no server involved.

Data tools include the JSON Formatter (format, validate, minify, sort), JSON Table Viewer (visualize JSON arrays as searchable sortable tables), JSON → TypeScript (generate interfaces from any JSON), JSON Dashboard Generator (instant charts and stat cards from JSON or API responses), SQL Formatter (beautify MySQL, PostgreSQL, and SQLite queries), and YAML ↔ JSON and CSV ↔ JSON converters. Security & encoding covers Hash Generator (MD5, SHA-1, SHA-256, SHA-512), Base64 Encoder/Decoder, JWT Decoder, URL Encoder/Decoder, and Password Generator with entropy scoring. API tools include API Request Generator & Tester (12 languages, live browser testing, cURL, Fetch, Axios, Python, Go) and API Mock Generator (fake REST endpoints with JSON schema). Utilities include Diff Checker, Regex Tester, UUID/ULID/NanoID Generator, Timestamp Converter, Cron Expression Builder, Meta Tag Generator, HTML Formatter, and Responsive Preview.

Frequently Asked Questions

Do any of these tools send my code or data to a server?: No. Every tool in this list processes data entirely in your browser using standard JavaScript APIs. JSON, code, passwords, JWT tokens, and API credentials never leave your device. Security-sensitive tools like Hash Generator and Password Generator use the browser's built-in SubtleCrypto API, which runs natively without network calls.
Can I test real API endpoints with the API Request Generator?: Yes. The API Request Generator & Tester lets you build requests with custom headers, body (JSON, form data, raw), authentication, and query parameters, then execute them live in the browser and inspect the response status, headers, and body. It generates equivalent code in 12 languages so you can copy a working snippet for your project.
What JWT claims does the JWT Decoder show?: The JWT Decoder splits any JWT into its three parts, base64-decodes the header and payload, and displays all claims with human-readable descriptions — including exp (expiry with live countdown), iat (issued at), nbf, sub, aud, iss, and any custom claims. It also verifies HS256 signatures if you provide the secret.
What UUID formats does the UUID generator support?: The UUID / ULID / NanoID generator supports UUID v4 (random), UUID v7 (time-ordered, sortable), UUID v1 (time-based with MAC address), ULID (Universally Unique Lexicographically Sortable Identifier), and NanoID with a custom alphabet. It generates up to 1,000 IDs at once with uppercase, no-hyphens, and copy-all options.
How does the Diff Checker work?: Paste two text blocks (code, JSON, prose, config) into the left and right panels. The tool uses LCS (Longest Common Subsequence) diffing to identify added, removed, and unchanged lines. Switch between split view (side by side), unified view (GitHub-style), and character-level inline highlighting to see exactly what changed.
Can I build fake API responses for frontend development?: Yes. The API Mock Generator lets you define JSON schema structures and generates realistic fake data (names, emails, dates, IDs, booleans). Export as a JSON Server db.json file to run a local mock REST API, or as a Postman collection for sharing with your team.

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