すべてのガイド
50個のガイドで無料オンラインツールを最大限に活用 — ステップバイステップのチュートリアル、詳細な説明、比較、ヒント。
How to Encode and Decode Base64 — 完全ガイド
Learn what Base64 encoding is, how it works, when to use it, and how to encode and decode Base64 in your browser —no tools or signup needed.
comparisonBase64 vs Hexエンコーディング：どちらを使うべきか？
Compare Base64 and Hex encoding across efficiency, readability, use cases, and trade-offs — and learn when to pick each for binary-to-text encoding.
explanationカラーフォーマット解説：HEX、RGB、HSL
Understand the three most common web color formats —HEX, RGB, and HSL —how each represents color, when to use which, and how to convert between them.
comparisonCSV vs TSV：どちらの区切り文字フォーマットを使うべきか？
Compare CSV and TSV across delimiter choice, escaping, compatibility, and use cases — and learn when to pick each for tabular data.
referenceDNSレコード解説：A、AAAA、MX、TXT、CNAME、NS
A complete reference guide to DNS record types —A, AAAA, MX, TXT, CNAME, and NS —with examples, use cases, and how to look them up.
explanationハッシュアルゴリズム解説：MD5、SHA-1、SHA-256、SHA-512
Understand cryptographic hash functions: differences between MD5, SHA-1, SHA-256, and SHA-512, and which to use for integrity checks vs password storage.
how-to使い方 Compress Images Without Losing Quality
Step-by-step guide to compressing images (JPEG, PNG, WebP) to reduce file size without visible quality loss using a free browser-based tool.
how-to使い方 Compress PDF Files Step by Step
Step-by-step guide to compressing PDF files to reduce file size using a free browser-based tool. Learn compression levels and what affects PDF size.
how-to使い方 Convert Colors Between HEX, RGB, and HSL
Step-by-step guide to converting colors between HEX, RGB, HSL, and other formats using a free browser-based tool. Learn when to use each format.
how-to使い方 Convert CSV to JSON Step by Step
Step-by-step guide to converting CSV data to JSON using a free browser-based tool. Learn header handling, nested structures, and common pitfalls.
how-to使い方 Convert Markdown to HTML Step by Step
Step-by-step guide to converting Markdown text to HTML using a free browser-based tool. Learn syntax, extensions, and common use cases.
how-to使い方 Convert Text to Binary and Back Step by Step
Step-by-step guide to converting text to binary (0s and 1s) and decoding binary back to text using a free browser-based tool. Learn ASCII and UTF-8.
how-to使い方 Convert Unix Timestamps to Human-Readable Dates (Step-by-Step)
Step-by-step guide to converting Unix timestamps (epoch) to human-readable dates and back using a free browser-based tool. Learn seconds vs milliseconds.
how-to使い方 Decode JWT Tokens and Inspect Claims Safely
Step-by-step guide to decoding JWT (JSON Web Token) tokens and inspecting their header and payload claims using a free browser-based tool. Learn security boundaries.
how-to使い方 Encode and Decode Base64 Strings Step by Step
Step-by-step guide to encoding text to Base64 and decoding Base64 back to text using a free browser-based tool. No upload, no signup, fully private.
how-to使い方 Encode and Decode URLs Step by Step
Step-by-step guide to URL encoding (percent-encoding) and decoding using a free browser-based tool. Learn why and when to encode URLs.
how-to使い方 Extract Text from PDF Files Step by Step
Step-by-step guide to extracting text content from a PDF file using a free browser-based tool. Learn scanned vs digital PDFs.
how-to使い方 Format and Validate JSON Data Step by Step
Step-by-step guide to formatting (beautifying) and validating JSON data using a free browser-based tool. Catch syntax errors, minify, and pretty-print JSON instantly.
how-to使い方 Generate Hash Values Step by Step
Step-by-step guide to generating cryptographic hash values (SHA-256, SHA-1, MD5) using a free browser-based tool. Learn use cases and security tradeoffs.
how-to使い方 Generate Secure Passwords Step by Step
Step-by-step guide to generating strong, random passwords using a free browser-based tool. Learn password length, character sets, and security best practices.
how-to使い方 Generate UUIDs Step by Step
Step-by-step guide to generating UUIDs (Universally Unique Identifiers) using a free browser-based tool. Learn UUID v4, v1, and when to use each.
how-to使い方 Merge PDF Files Step by Step
Step-by-step guide to merging (combining) multiple PDF files into one using a free browser-based tool. Learn ordering and page ranges.
how-to使い方 Resize Images Step by Step
Step-by-step guide to resizing images (change width and height) using a free browser-based tool. Learn aspect ratio, upscaling, and common dimensions.
how-to使い方 Split PDF Files Step by Step
Step-by-step guide to splitting a PDF file into multiple parts or extracting specific pages using a free browser-based tool.
how-to使い方 Test Regular Expressions Step by Step
Step-by-step guide to testing and debugging regular expressions using a free browser-based tool. Learn flags, capture groups, and common patterns.
how-to使い方 Use a Color Picker to Find Colors from Any Pixel
Step-by-step guide to using a color picker to find the exact color (HEX, RGB, HSL) of any pixel in an image or on screen using a free browser-based tool.
explanationJSONフォーマットのベストプラクティス：読みやすく、妥当で、効率的
Understand the conventions for formatting JSON: indentation, key ordering, minification, trailing commas, and when to pretty-print vs minify.
explanationJSONの理解：フォーマットと検証の初心者ガイド
JSONとは何か、その構文ルール、一般的なデータ型、そして無料のオンラインツールを使ってJSONデータをフォーマットおよび検証する方法を学びます。
comparisonJSON vs XML：どちらのデータフォーマットを使うべきか？
Compare JSON and XML across syntax, verbosity, parsing speed, ecosystem support, and use cases — and learn when to pick each.
comparisonJSON vs YAML：どちらの設定フォーマットを使うべきか？
Compare JSON and YAML across readability, features, use cases, and trade-offs — and learn when to pick each for configuration and data interchange.
how-to使い方 Decode a JWT and Inspect Its Claims Safely
Learn the three-part structure of a JSON Web Token, how to decode the header and payload without verifying, and why decoding is not the same as trusting.
comparisonMarkdown vs HTML：コンテンツにどちらを使うべきか？
Compare Markdown and HTML across readability, expressiveness, learning curve, use cases, and rendering —and learn when to pick each (or both).
problem-solvingパスワードセキュリティ：強力なパスワードの生成、保存、監査方法
Solve the most common password security problems: generating strong passwords, hashing them correctly, avoiding reuse, and auditing existing credentials.
comparisonPDF圧縮ツール vs 画像圧縮ツール：どちらが必要ですか？
Compare PDF and Image compression across targets, techniques, quality trade-offs, and use cases — and learn which tool to use for your file size problem.
reference正規表現チートシート：構文、フラグ、一般的なパターン
Complete regex reference: metacharacters, character classes, quantifiers, anchors, groups, flags, and ready-to-use patterns for emails, URLs, and dates.
how-to使い方 Convert Unix Timestamps to Human-Readable Dates
Learn what a Unix timestamp is, how to convert it to a human-readable date and back, and how to handle time zones correctly when working with epoch time.
reference単位換算リファレンス：長さ、質量、温度、面積
A complete reference of conversion factors for length, mass/weight, temperature, and area, with exact formulas and worked examples for each.
how-toHow to Encode and Decode URLs — 完全ガイド
Learn what URL encoding (percent-encoding) is, why it is required, and how to encode and decode URLs in your browser —no signup, fully private.
comparisonUUID v1 vs v4 vs v5：どのバージョンを使うべきか？
Compare UUID versions 1, 4, and 5: how each is generated, their trade-offs in uniqueness, ordering, and determinism, and which to pick for your use case.
explanationBase64エンコーディングとは？完全な解説
A clear explanation of what Base64 encoding is, how it works, its character set, and why it is not encryption.
explanationCSVとは？カンマ区切り値の完全な解説
A clear explanation of what CSV (Comma-Separated Values) is, its syntax rules, common variations, and when to use CSV vs JSON.
explanationハッシュとは？ハッシュ関数の完全な解説
A clear explanation of what hashing is, properties of cryptographic hash functions, common algorithms (SHA-256, MD5), and use cases.
explanationJSONとは？JavaScript Object Notationの完全な解説
A clear explanation of what JSON (JavaScript Object Notation) is, its syntax, data types, history, and why it replaced XML as the web's data format.
explanationJWTとは？JSON Web Tokenの完全な解説
A clear explanation of what a JWT (JSON Web Token) is, its three-part structure, how it is used for authentication, and security considerations.
explanationMarkdownとは？軽量マークアップ言語の完全な解説
A clear explanation of what Markdown is, its syntax, why it is popular for documentation, and how it converts to HTML.
explanation正規表現とは？完全な解説
A clear explanation of what a regular expression (regex) is, its syntax, common use cases, and why regex is powerful but hard to read.
explanationUnixタイムスタンプとは？エポック時間の完全な解説
A clear explanation of what a Unix timestamp is, the Unix epoch, seconds vs milliseconds, and the Year 2038 problem.
explanationURLエンコーディングとは？パーセントエンコーディングの完全な解説
A clear explanation of what URL encoding (percent-encoding) is, which characters need encoding, and how it works.
explanationUUIDとは？汎用一意識別子の完全な解説
A clear explanation of what a UUID is, its versions (v1, v4, v5), structure, collision probability, and when to use UUIDs.
how-to使い方 Count Words, Characters, and Reading Time Accurately
Learn how word and character counts are defined across languages, how to estimate reading time, and how to use a counter to hit limits for essays, tweets, and meta descriptions.