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Developer Online Tools

64 tools

Text 24 Developer 64 Design 28 Image 23 Documents 12 Calculator 60 Video 6 Finance 26 Random 7 Utility 8

JSON Formatter

Format and validate JSON with syntax highlighting

Password Generator

Generate secure random passwords with one click

UUID Generator

Generate UUID v4 in bulk with format options

ASCII Converter

Convert between text and ASCII/Unicode codes

Base64 Encoder

Encode and decode text or files to Base64

URL Encoder

Encode and decode URL special characters

IP Address Checker

Check your global IP address

Color Converter

Convert between HEX, RGB, and HSL colors

Hash Generator

Generate MD5, SHA-1, SHA-256 and other hashes

Number Base Converter

Convert between binary, octal, decimal, and hex

Decimal Base Converter

Convert fractions such as 0.1 to binary, octal and hex, with repeating digits, error and steps

Regex Checker Tool

Test regex in real-time with match highlighting, explanations & pattern library

Unix Timestamp Converter

Convert Unix timestamps to dates instantly. Auto-detect s/ms, multiple formats, code snippets for 10 languages

Case Converter

Convert to camelCase, snake_case, kebab-case & more in bulk

JWT Decoder

Decode JWT header & payload with expiry check, all in-browser

Crontab Generator

Build cron expressions with human-readable text & next runs

Markdown Editor & Preview

Live Markdown preview with HTML export, all in-browser

JSON / CSV Converter

Convert between JSON and CSV with delimiter & header options

Meta Tag & OGP Generator

Generate meta, OGP & Twitter Card tags with live preview

Image to Base64

Convert images to Base64 data URI and back, with snippets

HTML Entity Converter

Encode and decode HTML entities & escape special characters

Markdown Table Generator

Build Markdown tables from a grid or CSV, with alignment

Slug Generator

Generate URL slugs from text with romaji & separators

Unicode Inspector

Inspect each character: code point, UTF-8 bytes & entity

Password Strength Checker

Check password strength & crack time, all in your browser

SQL Formatter

Format & minify SQL with dialect support, all in-browser

Text Encrypt / Decrypt

AES-encrypt/decrypt text with a passphrase, fully in-browser

JSON to TypeScript

Generate TypeScript interfaces/types from JSON, nested support

JSON Diff

Compare two JSON objects and highlight differences recursively

User Agent Parser

Detect browser, OS & device from your or any user agent

AI Token Counter

Estimate tokens for GPT/Claude/Gemini with API cost calculation

JSON / YAML Converter

Convert between JSON and YAML with formatting & indent options

HTTP Status Codes Reference

Reference for all HTTP status codes with search & copy

cURL Converter

Convert cURL commands to fetch, Python & more, in-browser

TOML / JSON Converter

Convert between TOML and JSON with formatting

.env Converter

Convert between .env, JSON and YAML formats

Prompt Template Builder

Build reusable AI prompt templates with variables, in-browser

Text Binary Converter

Convert text to/from binary, octal & hex (UTF-8)

File to Base64 Converter

Convert any file to/from Base64 / data URI, in-browser

chmod Permissions Calculator

Convert chmod numeric (755) and symbolic (rwxr-xr-x) values

CSV Viewer

View, sort, search & clean CSV/TSV, export to JSON & more

JSONPath Tester

Test JSONPath expressions against JSON and view matches

CIDR Subnet Calculator

Calculate network, broadcast & host range from IP/CIDR

Code Minifier

Minify CSS, JS & HTML to reduce size, all in-browser

Text Encoding Converter

Convert text between Shift_JIS, EUC-JP, UTF-8 & more

Mermaid Diagram Editor

Create diagrams from Mermaid syntax, export SVG/PNG

Number Formatter

Format numbers with separators, decimals, currency & rounding

Markdown TOC Generator

Generate a linked table of contents from Markdown headings

Newline (Line Ending) Converter

Convert line endings between CRLF, LF, and CR

Tab / Space Converter

Convert indentation between tabs and spaces

JSON String Escape / Unescape

Escape and unescape strings for JSON

URL Parser

Break a URL into scheme, host, path, and query

Hex ↔ Text Converter

Convert between text and UTF-8 hexadecimal

Naming Case Converter

Convert between camelCase, snake_case, kebab-case, etc.

MIME Type Finder

Look up MIME type by file extension and vice versa

Scientific Notation Converter

Convert between decimal and scientific (E) notation

Data Size Converter

Convert between bits, bytes, KB, MB, GB, etc.

XML Formatter

Pretty-print and minify XML

HTML to Markdown Converter

Convert HTML into Markdown

Bitwise Calculator

Compute AND, OR, XOR, NOT, and bit shifts

JSON ⇔ XML Converter

Convert between JSON and XML

Query String Converter

Convert query strings to/from JSON and a table

Markdown to HTML Converter

Convert Markdown to HTML with preview

HTML Formatter

Beautify and minify HTML

Related Guides

What Is JSON? A Beginner Guide to Syntax, Writing, and Common Errors Learn what JSON is from the ground up: objects and arrays, the data types you can use, common syntax errors like trailing commas, and practical uses such as formatting, validation, YAML conversion, and diffing. Regular Expressions for Beginners: Metacharacters and How to Write Regex Learn how to write regular expressions from scratch: the core metacharacters . * + ? [] () | ^ $, quantifiers, common patterns for email, phone, and URLs, groups and replacement, and tips for learning regex. What Is Base64? How It Works, Its Uses, URL-Safe Encoding, and Size Growth Learn what Base64 is from the basics: how it turns 3 bytes into 4 characters, its uses in data URIs, email attachments, and API tokens, URL-safe encoding, and why the data grows about 1.33x, plus key caveats. Markdown for Beginners: How to Write Headings, Lists, Links, and Tables A beginner guide to writing Markdown. Learn the core syntax for headings, lists, links, emphasis, code, and tables, plus how to export to HTML and PDF and use Markdown on GitHub and blogs. What Is a Hash? MD5, SHA-1, and SHA-256 Differences and Uses Explained Learn what a hash value is from the ground up: properties like one-way and fixed-length, the differences between MD5, SHA-1, and SHA-256, uses in tamper detection and password storage, salting, how it differs from encryption, and collision risks. What Is a Unix Timestamp? Epoch Seconds Since 1970 Explained Simply Learn what a Unix timestamp (epoch time) is from the ground up: the meaning of seconds since 1970, its relationship to time zones, milliseconds, the Year 2038 problem, and converting to and from human dates. What Is a UUID? v1 vs v4, How Uniqueness Works, and Collision Odds Learn what a UUID is from the ground up: the 128-bit structure, the difference between v1 and v4, why values do not collide, collision probability, uses such as database primary keys, and how it differs from auto-increment serial IDs. How to Write Cron: The 5 Fields, Symbols, and crontab Examples Explained Learn how to write cron (crontab) from scratch: the meaning of the five fields (minute, hour, day, month, weekday), how to use * / , -, common examples like daily, hourly, and weekly, and pitfalls to watch for. What Is a JWT? JSON Web Token Structure, Signing, and Verification Explained Learn what a JWT (JSON Web Token) is from the ground up: the header.payload.signature structure, Base64URL encoding, how signing and verification work, the exp expiration claim, and why you must never put secrets inside it. What Is CSV? Delimiters, Quotes, and How to Avoid Garbled Text Learn what CSV is from the ground up: comma delimiters, quoting, line breaks, why text gets garbled when you open files in Excel and how to avoid it, plus practical uses like viewing and JSON conversion. Data Size Units Explained: KB, MB, GB and Bytes vs bps A clear guide to bits and Bytes, the KB–MB–GB–TB ladder, the 1000-vs-1024 difference (KiB, MiB), how bps connection speed relates, and typical file sizes—including why "1 TB shows as 931 GB." What Is an IP Address? Subnets and CIDR (/24) Made Simple A beginner-friendly guide to IP addresses and subnets: the 32-bit structure of IPv4, private vs. global addresses, CIDR notation such as /24, subnet masks, and network and broadcast addresses. What Is OGP? Meta Tag Basics, og:image Size, and How Social Cards Work A beginner-friendly guide to OGP (Open Graph Protocol) and meta tags: the roles of title and description, the meaning of og:title, og:image, og:type, and twitter:card, how social platforms build share cards, the recommended 1200x630 image size, and how to verify your settings. What Is Dummy Text (Lorem Ipsum)? Why Meaningless Text, Its Origin, and Uses Learn what dummy text (Lorem Ipsum) is from the ground up: the meaningless Latin-like text used in place of real copy, why meaningless text is used on purpose, its surprisingly old origin, uses in mockups and typesetting checks, and how it differs from Japanese dummy text. How to Write URL Slugs: SEO-Friendly Rules and Non-English URL Pitfalls Learn what a URL slug is from the ground up: how it relates to SEO, the basic rules of lowercase letters, hyphen separators, and short meaningful words, the encoding problem with non-English URLs, symbols to avoid, and redirect cautions when changing a slug after publishing. Intro to Mermaid: Draw Diagrams from Text — Flowcharts, Sequence Diagrams, and Gantt Learn what Mermaid is from the ground up: how text turns into diagrams, the basic syntax for flowcharts (graph TD), sequence diagrams, and Gantt charts, how to write nodes and arrows, how to use it in GitHub and Notion, and the benefits of managing diagrams as code. Understanding URL Structure: Scheme, Host, Path, Query, and Fragment Learn URL structure from the ground up: the role of the scheme (https), host, port, path, query string (?key=value&), and fragment (#), how percent-encoding works, and the difference between absolute and relative URLs, explained for beginners. Character Encoding and UTF-8 Basics: ASCII vs Shift_JIS and Mojibake A beginner-friendly guide to character encoding: the difference between ASCII, Shift_JIS, and UTF-8, how UTF-8 uses a variable length (1 to 4 bytes), what a BOM is, why UTF-8 became the world standard, and why garbled text (mojibake) happens. Scientific Notation (E Notation) and Significant Figures Basics A beginner-friendly guide to scientific (E) notation and significant figures: how to read forms like 1.5e3, how to express very large and very small numbers, counting significant figures, rounding, E notation in Excel and programming, and overflow. CSV vs TSV: Delimiters, Quoting, Encoding, and When to Use Each A clear guide to the difference between CSV and TSV: comma vs tab delimiters, how quoting handles values containing commas or line breaks, character encoding pitfalls, tips for importing CSV into Excel, when TSV is handy, and how both compare to JSON. How to Read Roman Numerals: Meaning of I V X L C D M and the Rules Learn how to read Roman numerals from the basics: what the seven letters I, V, X, L, C, D, and M mean, the additive and subtractive rules (IV=4, IX=9), how to write large numbers, use on clocks and in years, tips for converting to Arabic numerals, and why you cannot write 4000 or more. What Is a Number Base? Binary, Octal, and Hex Basics Made Simple Learn the basics of number bases (binary, octal, hex): why computers use binary, the 0b/0o/0x notation, how to convert to and from decimal, the relationship between bits and bytes, and why hex is used for things like color codes. Naming Conventions and Case Styles: camelCase vs snake_case vs kebab-case A beginner-friendly guide to programming naming conventions. Learn the differences between camelCase, snake_case, kebab-case, PascalCase, and CONSTANT_CASE, per-language conventions in JavaScript, Python, and CSS, how to choose for variables, functions, constants, and file names, and tips for readability. Password Management Basics: Reuse Risks, Strong Passwords, Managers, and 2FA Learn the basics of safe password management: why reusing passwords is dangerous, what makes a password strong (length and complexity), memorable passphrases, using a password manager, two-factor authentication, anti-phishing tips, and how to check for breaches. How to Write Markdown Tables: Pipes, Hyphens, Alignment, and Line Breaks Learn how to write Markdown tables from the basics: building header and separator rows with pipes (|) and hyphens (-), left/center/right alignment set by the colon (:) position, line breaks and pipe escaping inside cells, and how tables render on GitHub and in Notion, with examples. What Is a MIME Type? The Content-Type Header, type/subtype, and charset Learn what a MIME type (content type) is from the ground up: the role of the Content-Type header, the type/subtype format such as text/html and image/png, the charset parameter for character encoding, browser behavior, the relationship with file extensions, and a list of common MIME types. What Is XML? Structure, How It Differs From HTML, Uses, and JSON Comparison Learn what XML is from the ground up: a markup language that expresses hierarchy with tags, the structure of elements, attributes, and text, the well-formed rules, how it differs from HTML, uses such as configuration, data exchange, RSS, and SVG, and a comparison with JSON. Data Size Units Explained: KB, MB, GB and the 1000 vs 1024 Difference Learn data size units from the ground up: the relationship between bits and bytes, the meaning of KB, MB, and GB, the difference between SI prefixes (1000) and binary prefixes like KiB and MiB (1024), why storage and OS figures differ, how it differs from bps speed, and rough size references. What Is ASCII? 7 Bits for 128 Characters, Control vs. Printable, and A=65 Learn what ASCII is from the ground up: how 7 bits represent 128 characters, the difference between control and printable characters, the A=65 / a=97 / 0=48 mapping rules, extended ASCII, the relationship with Unicode and UTF-8, and how to convert between characters and numbers. Common Regex Patterns: Email, Phone, URL, ZIP, Date Examples and Pitfalls Practical regular expression patterns for everyday use, with examples for email, phone number, URL, postal code, date, and full-width/half-width text. Covers metacharacters, quantifiers, and groups, plus why you should not over-trust regex. Converting HTML to Markdown: Supported Elements, Pitfalls, and When to Edit by Hand A clear guide to converting HTML to Markdown: why you convert it for CMS migration and republishing, which elements convert (headings, links, lists, tables, code, images), what breaks or cannot convert, and how to balance automatic conversion with manual editing. What Are HTML Entities? Escaping < > & and Special Characters Learn what HTML entities (character references) are from the ground up: why you cannot write < > & directly, named vs numeric references, a list of common entities, handling quotes inside attribute values, and how they relate to mojibake and XSS. What Is a REST API? HTTP Methods, Endpoints, and Status Codes Explained Learn the basics of REST APIs from scratch: what an API is, the REST approach, HTTP methods like GET/POST/PUT/DELETE, endpoints and resource design, status codes, JSON requests and responses, query parameters, and an overview of authentication. Bitwise Operations Basics: AND, OR, XOR, NOT, Shifts, and Masks Explained Learn the basics of bitwise operations from scratch: the AND, OR, XOR, and NOT logic operations, left and right shifts, how to set and clear individual bits, masks and flag management, the link to powers of two, and real uses like permissions, color, and optimization. What Is Two's Complement? Representing Negatives, Invert-and-Add-One, and Ranges Learn two's complement from the ground up: how computers represent negative numbers, the invert-the-bits-and-add-one method, the role of the sign bit, overflow, and the ranges representable in 8/16/32 bits. Network Speed Basics: bps vs Byte/s, Mbps, Real Speed & Download Time Learn network speed basics in plain terms: the difference between bps (bits per second) and Byte/s, how to read Mbps and Gbps, why real-world speed is slower than advertised, and how to estimate download time from a file size in GB. Converting Between JSON and XML: Structure Mapping, Lost Data, and When to Use Each A clear guide to converting between JSON and XML: how objects, arrays, and attributes map to each other, information that is easily lost in conversion, when to use each format, and pitfalls around attributes, namespaces, and types. JSON vs XML vs YAML: Differences, Syntax, Types, and When to Use Each A clear comparison of JSON, XML, and YAML: their syntax, readability, comment support, and handling of types, plus which fits config files, data exchange, and APIs, how to convert between them, and a simple guide to choosing one. What Are Escape Sequences? Meaning of \n, \t, \\, \" and Language Differences Learn what escape sequences are from the ground up: how characters with special meaning like newline (\n), tab (\t), backslash (\\), and quote (\") work, differences between languages, escaping in JSON, and common bugs and fixes for beginners. What Is a Query String? The ?key=value Structure, Multiple Values, and Percent-Encoding Learn what a query string (query parameters) is from the ground up: the ?key=value&... structure, how to express multiple values and arrays, percent-encoding, how it is used with GET, and design pitfalls such as order, duplication, and length. Converting Markdown to HTML: Syntax Mapping, How It Works, Safe Output Learn how to convert Markdown to HTML from the ground up: how syntax like headings, paragraphs, lists, links, images, code, and tables maps to HTML tags, how conversion works, uses in blogs and CMSs, and how sanitization keeps the HTML output safe. HTML Formatting and Indentation: Readable Code, Nesting, vs. Minify Learn HTML formatting and indentation from the ground up: how to choose an indent width, make readable code, visualize nesting, why formatting matters, how it differs from minify and when to use each, attribute line-break rules, and where auto-formatters help. Minify vs Beautify: The Difference, When to Use Each, Source Maps & Reversibility Learn the difference between minifying and beautifying code: minify shrinks file size for production, beautify improves readability for development. Covers when to use each, source maps, reversibility, and where they fit in the build pipeline. HTML5 Semantic Tags Explained: header, nav, main, article, section, and SEO A beginner-friendly guide to HTML5 semantic tags: the role of header, nav, main, article, section, aside, and footer, how they differ from div, their effect on SEO and accessibility (screen readers), and how to think about correct markup. How to Create Strong Passwords: Length, Passphrases, and Management Learn how to build secure passwords from the ground up: why length beats complexity, the danger of reuse, memorable passphrases, the entropy metric, and using two-factor authentication and password managers.